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45 vulnerabilities by nltk
CVE-2026-81727 (GCVE-0-2026-81727)
Vulnerability from cvelistv5 – Published: 2026-08-27 14:51 – Updated: 2026-08-27 17:43
VLAI
EPSS
VEX
Title
NLTK before 3.10.3 Hardlink File Overwrite via downloader
Summary
NLTK versions before 3.10.3 contain a filesystem containment bypass vulnerability in the Downloader.download and Downloader.incr_download methods that allows attackers to overwrite files outside the install root through pre-existing hardlinks. Attackers with write access to a shared downloader directory can create hardlinks pointing to outside-root files that are then overwritten during normal package extraction, mutating files outside the intended install tree.
Severity
SSVC
Exploitation: poc
Automatable: no
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-08-27 17:43 UTC
CWE
- CWE-59 - Improper Link Resolution Before File Access ('Link Following')
Assigner
References
2 references
| URL | Tags |
|---|---|
| https://github.com/nltk/nltk/security/advisories/… | vendor-advisory |
| https://www.vulncheck.com/advisories/nltk-before-… | third-party-advisory |
Impacted products
Date Public
2026-08-12 00:00
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CVE-2026-81726 (GCVE-0-2026-81726)
Vulnerability from cvelistv5 – Published: 2026-08-27 14:51 – Updated: 2026-08-27 19:29
VLAI
EPSS
VEX
Title
NLTK through 3.10.3 Path Traversal via Model-Artifact APIs
Summary
NLTK through 3.10.3 contains a path traversal vulnerability in model-artifact APIs that bypass pathsec enforcement by using raw file operations on caller-controlled paths. Attackers can read or write files outside allowed sandbox roots through TransitionParser, AveragedPerceptron, PerceptronTagger, and maxent parameter APIs when pathsec is enabled.
Severity
SSVC
Exploitation: poc
Automatable: no
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-08-27 19:29 UTC
CWE
- CWE-73 - External Control of File Name or Path
Assigner
References
2 references
| URL | Tags |
|---|---|
| https://github.com/nltk/nltk/security/advisories/… | vendor-advisory |
| https://www.vulncheck.com/advisories/nltk-through… | third-party-advisory |
Impacted products
Date Public
2026-08-12 00:00
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CVE-2026-81725 (GCVE-0-2026-81725)
Vulnerability from cvelistv5 – Published: 2026-08-27 14:51 – Updated: 2026-08-28 15:58
VLAI
EPSS
VEX
Title
NLTK before 3.10.3 Regular Expression Denial of Service via Pl196xCorpusReader
Summary
NLTK before 3.10.3 contains a regular expression denial of service vulnerability in Pl196xCorpusReader that allows attackers to cause quadratic CPU consumption by supplying malformed TEI blocks with many unmatched opening tags. Attackers can exploit lazy regex patterns in the read_block method through public APIs like words() and tagged_words() to force repeated rescans and achieve near-quadratic runtime growth.
Severity
SSVC
Exploitation: none
Automatable: no
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-08-27 18:24 UTC
CWE
- CWE-400 - Uncontrolled Resource Consumption
Assigner
References
2 references
| URL | Tags |
|---|---|
| https://github.com/nltk/nltk/security/advisories/… | vendor-advisory |
| https://www.vulncheck.com/advisories/nltk-before-… | third-party-advisory |
Impacted products
Date Public
2026-08-12 00:00
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CVE-2026-81724 (GCVE-0-2026-81724)
Vulnerability from cvelistv5 – Published: 2026-08-27 14:51 – Updated: 2026-08-27 18:29
VLAI
EPSS
VEX
Title
NLTK before 3.10.3 Denial of Service via Uncontrolled Recursion
Summary
NLTK before 3.10.3 contains an uncontrolled recursion vulnerability in nltk.featstruct.FeatStructReader that allows unauthenticated attackers to cause a denial of service by supplying deeply nested feature-structure input. Attackers can craft trivial payloads with nested brackets that exceed Python's recursion limit and raise an unhandled RecursionError, crashing applications that parse user-supplied feature structures or feature grammars.
Severity
5.3 (Medium)
SSVC
Exploitation: poc
Automatable: yes
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-08-27 18:28 UTC
CWE
- CWE-674 - Uncontrolled Recursion
Assigner
References
2 references
| URL | Tags |
|---|---|
| https://github.com/nltk/nltk/security/advisories/… | vendor-advisory |
| https://www.vulncheck.com/advisories/nltk-before-… | third-party-advisory |
Impacted products
Date Public
2026-08-12 00:00
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CVE-2026-81723 (GCVE-0-2026-81723)
Vulnerability from cvelistv5 – Published: 2026-08-27 14:51 – Updated: 2026-08-31 18:12
VLAI
EPSS
VEX
Title
NLTK before 3.10.3 Quadratic CPU Exhaustion via XMLCorpusView
Summary
NLTK versions before 3.10.3 contain a quadratic CPU exhaustion vulnerability in XMLCorpusView._read_xml_fragment() that rescans accumulated XML fragments on every 1 KiB block read. Attackers can provide malformed XML corpus files to cause severe CPU consumption and denial of service through affected readers like BNCCorpusReader.
Severity
SSVC
Exploitation: poc
Automatable: no
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-08-31 18:12 UTC
CWE
- CWE-400 - Uncontrolled Resource Consumption
Assigner
References
2 references
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| https://github.com/nltk/nltk/security/advisories/… | vendor-advisory |
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Impacted products
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2026-08-12 00:00
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CVE-2026-81722 (GCVE-0-2026-81722)
Vulnerability from cvelistv5 – Published: 2026-08-27 14:51 – Updated: 2026-08-27 17:49
VLAI
EPSS
VEX
Title
nltk PorterStemmer before 3.10.3 Quadratic-time DoS
Summary
nltk PorterStemmer in versions <= 3.10.2 (fixed in 3.10.3) contains an inefficient-algorithmic-complexity denial of service in PorterStemmer.stem(). The _is_consonant() helper walks backward over the entire run of trailing 'y' characters on every call, and _measure() invokes it for each stem position, causing O(n^2) behavior. A single ~20-50 KB untrusted token consisting of a long run of the letter 'y' followed by a matching suffix (e.g., 'ness') can pin a CPU core for seconds to minutes, causing availability impact.
Severity
SSVC
Exploitation: poc
Automatable: yes
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-08-27 17:49 UTC
CWE
- CWE-407 - Inefficient Algorithmic Complexity
Assigner
References
2 references
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|---|---|
| https://github.com/nltk/nltk/security/advisories/… | vendor-advisory |
| https://www.vulncheck.com/advisories/nltk-porters… | third-party-advisory |
Impacted products
Date Public
2026-08-12 00:00
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CVE-2026-80206 (GCVE-0-2026-80206)
Vulnerability from cvelistv5 – Published: 2026-08-26 10:28 – Updated: 2026-08-26 12:52
VLAI
EPSS
VEX
Title
NLTK 3.10.2 Regular Expression Denial of Service via tgrep
Summary
NLTK before 3.10.3 contains a regular expression denial of service (ReDoS) vulnerability in the tgrep module. The _tgrep_node_action function compiles user-supplied regular expressions embedded in /regex/ pattern nodes and executes them via re.search against tree node labels without any validation or timeout. An attacker who controls the tgrep pattern (e.g., via tgrep_positions() or tgrep_compile() exposed to external input) can supply a pattern that triggers catastrophic backtracking, causing indefinite CPU saturation that blocks the Python process.
Severity
SSVC
Exploitation: poc
Automatable: no
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-08-26 12:52 UTC
CWE
- CWE-1333 - Inefficient Regular Expression Complexity
Assigner
References
2 references
| URL | Tags |
|---|---|
| https://github.com/nltk/nltk/security/advisories/… | vendor-advisory |
| https://www.vulncheck.com/advisories/nltk-3.10.2-… | third-party-advisory |
Impacted products
Date Public
2026-08-12 00:00
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CVE-2026-80205 (GCVE-0-2026-80205)
Vulnerability from cvelistv5 – Published: 2026-08-26 10:28 – Updated: 2026-09-01 22:06
VLAI
EPSS
VEX
Title
NLTK before 3.10.0 ReDoS via Text.findall() unvalidated regex
Summary
NLTK versions before 3.10.0 contain a regular expression denial of service vulnerability in Text.findall() and TokenSearcher.findall() methods that accept user-supplied regular expressions without validation or timeout. Attackers can supply crafted regex patterns that cause catastrophic backtracking, resulting in indefinite CPU saturation and denial of service to all users of the Python process.
Severity
SSVC
Exploitation: none
Automatable: yes
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-08-26 15:58 UTC
CWE
- CWE-1333 - Inefficient Regular Expression Complexity
Assigner
References
3 references
| URL | Tags |
|---|---|
| https://github.com/nltk/nltk/security/advisories/… | vendor-advisory |
| https://www.vulncheck.com/advisories/nltk-before-… | third-party-advisory |
| http://www.openwall.com/lists/oss-security/2026/09/01/3 |
Impacted products
Date Public
2026-08-12 00:00
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CVE-2026-79676 (GCVE-0-2026-79676)
Vulnerability from cvelistv5 – Published: 2026-08-25 15:16 – Updated: 2026-08-25 16:15
VLAI
EPSS
VEX
Title
NLTK before 3.10.3 Path Traversal via Symlink Bypass
Summary
NLTK versions before 3.10.3 contain a path traversal vulnerability in corpus readers that reopen root-derived paths using built-in open() instead of nltk.pathsec.open(), allowing symlinks to escape trusted roots. Attackers who stage symlinked corpus files under a trusted data root can disclose outside-root content through normal corpus reader methods like channels(), domains(), and synonyms().
Severity
SSVC
Exploitation: poc
Automatable: no
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-08-25 16:14 UTC
CWE
- CWE-22 - Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
Assigner
References
2 references
| URL | Tags |
|---|---|
| https://github.com/nltk/nltk/security/advisories/… | vendor-advisory |
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Impacted products
Date Public
2026-08-11 00:00
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CVE-2026-79675 (GCVE-0-2026-79675)
Vulnerability from cvelistv5 – Published: 2026-08-25 15:16 – Updated: 2026-08-27 16:24
VLAI
EPSS
VEX
Title
NLTK before 3.10.3 JVM Argument Injection via Per-Call Options
Summary
NLTK before 3.10.3 fails to validate JVM options passed through the per-call options parameter in the java() function, allowing attackers to inject dangerous JVM flags. Attackers can supply malicious options like -agentpath, -javaagent, or @argfile to Stanford wrapper classes to achieve arbitrary code execution.
Severity
9.8 (Critical)
SSVC
Exploitation: poc
Automatable: yes
Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-08-26 03:56 UTC
CWE
- CWE-88 - Improper Neutralization of Argument Delimiters in a Command ('Argument Injection')
Assigner
References
2 references
| URL | Tags |
|---|---|
| https://github.com/nltk/nltk/security/advisories/… | vendor-advisory |
| https://www.vulncheck.com/advisories/nltk-before-… | third-party-advisory |
Impacted products
Date Public
2026-08-11 00:00
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CVE-2026-79674 (GCVE-0-2026-79674)
Vulnerability from cvelistv5 – Published: 2026-08-25 15:16 – Updated: 2026-08-25 17:42
VLAI
EPSS
VEX
Title
NLTK 3.10.2 Path Traversal via corpus-reader constructors
Summary
NLTK versions before 3.10.3 contain a path sandbox bypass vulnerability in corpus-reader constructors that allows attackers to read files outside the intended data root. Attackers can supply arbitrary corpus root paths to LinThesaurusCorpusReader and PanLexLiteCorpusReader constructors to access filesystem content and SQLite databases outside the pathsec sandbox boundary.
Severity
SSVC
Exploitation: poc
Automatable: yes
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-08-25 17:42 UTC
CWE
- CWE-73 - External Control of File Name or Path
Assigner
References
2 references
| URL | Tags |
|---|---|
| https://github.com/nltk/nltk/security/advisories/… | vendor-advisory |
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Impacted products
Date Public
2026-08-11 00:00
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CVE-2026-79657 (GCVE-0-2026-79657)
Vulnerability from cvelistv5 – Published: 2026-08-25 11:33 – Updated: 2026-08-25 15:58
VLAI
EPSS
VEX
Title
NLTK before 3.10.3 Remote Code Execution via Unsafe Pickle Deserialization
Summary
NLTK versions before 3.10.3 contain a remote code execution vulnerability in allowlisted pickle loaders that trust entire module namespaces instead of specific safe callables. Attackers can craft malicious pickle payloads invoking dangerous in-namespace functions like ReppTokenizer._execute and numpy.f2py.crackfortran.myeval through pickle REDUCE to execute arbitrary commands during model or tokenizer artifact loading.
Severity
9.8 (Critical)
SSVC
Exploitation: poc
Automatable: yes
Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-08-25 15:58 UTC
CWE
- CWE-502 - Deserialization of Untrusted Data
Assigner
References
2 references
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|---|---|
| https://github.com/nltk/nltk/security/advisories/… | vendor-advisory |
| https://www.vulncheck.com/advisories/nltk-before-… | third-party-advisory |
Impacted products
Date Public
2026-08-11 00:00
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CVE-2026-78683 (GCVE-0-2026-78683)
Vulnerability from cvelistv5 – Published: 2026-08-25 01:30 – Updated: 2026-08-25 15:19
VLAI
EPSS
VEX
Title
NLTK before 3.10.0 Remote Code Execution via Unsafe Pickle Deserialization
Summary
NLTK before 3.10.0 (affected versions <=3.9.4) contains an unsafe pickle deserialization vulnerability in the TransitionParser.parse() method (nltk/parse/transitionparser.py). The method calls pickle_load() with the default restricted=False, routing deserialization through WarningUnpickler, which does not override find_class() and therefore permits arbitrary class resolution. When an application loads an attacker-crafted model file, embedded pickle gadget chains execute arbitrary Python code with the privileges of the user running the application. NLTK provides a RestrictedUnpickler for safe deserialization, but it is not used by production code paths. Fixed in 3.10.0.
Severity
9.6 (Critical)
SSVC
Exploitation: poc
Automatable: no
Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-08-25 15:19 UTC
CWE
- CWE-502 - Deserialization of Untrusted Data
Assigner
References
2 references
| URL | Tags |
|---|---|
| https://github.com/nltk/nltk/security/advisories/… | vendor-advisory |
| https://www.vulncheck.com/advisories/nltk-before-… | third-party-advisory |
Impacted products
Date Public
2026-08-11 00:00
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CVE-2026-78682 (GCVE-0-2026-78682)
Vulnerability from cvelistv5 – Published: 2026-08-25 01:30 – Updated: 2026-08-25 15:23
VLAI
EPSS
VEX
Title
NLTK before 3.10.3 SSRF Protection Bypass via Proxy
Summary
NLTK before 3.10.3 contains a server-side request forgery vulnerability in nltk.pathsec.urlopen (and callers nltk.data.load, nltk.downloader.Downloader.index/download) when an HTTP proxy is configured. pathsec.urlopen validates the requested hostname locally, but proxy-handler inheritance disables the safe HTTP/HTTPS handlers so the actual fetch is performed by the proxy against a destination that is never re-validated. An attacker can supply a validated public URL that the proxy forwards to an internal loopback-only service, allowing disclosure of internal HTTP resources, loading of forged downloader indexes, and installation of attacker-chosen package content.
Severity
SSVC
Exploitation: poc
Automatable: yes
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-08-25 15:23 UTC
CWE
- CWE-918 - Server-Side Request Forgery (SSRF)
Assigner
References
2 references
| URL | Tags |
|---|---|
| https://github.com/nltk/nltk/security/advisories/… | vendor-advisory |
| https://www.vulncheck.com/advisories/nltk-before-… | third-party-advisory |
Impacted products
Date Public
2026-08-11 00:00
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CVE-2026-78681 (GCVE-0-2026-78681)
Vulnerability from cvelistv5 – Published: 2026-08-25 01:30 – Updated: 2026-08-26 16:12
VLAI
EPSS
VEX
Title
NLTK before 3.10.3 Entity Expansion DoS via ElementTree
Summary
NLTK versions before 3.10.3 use xml.etree.ElementTree to parse XML in multiple modules, which honors entity declarations in document DTDs. Attackers can craft XML payloads with nested entity declarations that expand from hundreds of bytes to megabytes in memory, causing denial of service.
Severity
SSVC
Exploitation: none
Automatable: yes
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-08-26 15:58 UTC
CWE
- CWE-776 - Improper Restriction of Recursive Entity References in DTDs ('XML Entity Expansion')
Assigner
References
2 references
| URL | Tags |
|---|---|
| https://github.com/nltk/nltk/security/advisories/… | vendor-advisory |
| https://www.vulncheck.com/advisories/nltk-before-… | third-party-advisory |
Impacted products
Date Public
2026-08-11 00:00
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CVE-2026-78680 (GCVE-0-2026-78680)
Vulnerability from cvelistv5 – Published: 2026-08-25 01:30 – Updated: 2026-08-25 12:43
VLAI
EPSS
VEX
Title
NLTK before 3.10.3 Arbitrary Code Execution via Graphviz dot Binary
Summary
NLTK versions before 3.10.3 fail to use validated absolute paths when invoking the Graphviz dot binary in dependencygraph.dot2img and AlignedSent._repr_svg_, allowing attackers to execute arbitrary code by placing a malicious dot binary in the search path or current working directory. Attackers can exploit bare-name binary resolution on Windows via the current working directory or on Unix-like systems via relative PATH entries to execute their binary instead of the legitimate Graphviz tool.
Severity
SSVC
Exploitation: poc
Automatable: no
Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-08-25 12:29 UTC
CWE
- CWE-426 - Untrusted Search Path
Assigner
References
2 references
| URL | Tags |
|---|---|
| https://github.com/nltk/nltk/security/advisories/… | vendor-advisory |
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Impacted products
Date Public
2026-08-11 00:00
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CVE-2026-70626 (GCVE-0-2026-70626)
Vulnerability from cvelistv5 – Published: 2026-08-22 14:12 – Updated: 2026-08-24 19:49
VLAI
EPSS
VEX
Title
NLTK before 3.9.4 Symlink Escape via CorpusReader
Summary
NLTK versions before 3.9.4 contain a symlink escape vulnerability in CorpusReader.open() that allows local attackers to read arbitrary files outside the corpus root. The vulnerability exists because path validation is lexical and does not account for symlink resolution, enabling attackers to place symlinks inside the corpus root to access files outside the intended boundary.
Severity
SSVC
Exploitation: poc
Automatable: no
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-08-24 19:49 UTC
CWE
- CWE-59 - Improper Link Resolution Before File Access ('Link Following')
Assigner
References
2 references
| URL | Tags |
|---|---|
| https://github.com/nltk/nltk/security/advisories/… | vendor-advisory |
| https://www.vulncheck.com/advisories/nltk-before-… | third-party-advisory |
Impacted products
Date Public
2026-08-07 00:00
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CVE-2026-66393 (GCVE-0-2026-66393)
Vulnerability from cvelistv5 – Published: 2026-08-22 14:12 – Updated: 2026-08-26 17:55
VLAI
EPSS
VEX
Title
NLTK before 3.9.4 Denial of Service via JSONTaggedDecoder
Summary
NLTK versions before 3.9.4 contain an unbounded recursion vulnerability in JSONTaggedDecoder.decode_obj() that allows attackers to cause denial of service by supplying deeply nested JSON structures. Attackers can craft JSON payloads exceeding the recursion limit to trigger an unhandled RecursionError that crashes the Python process.
Severity
SSVC
Exploitation: poc
Automatable: yes
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-08-26 17:54 UTC
CWE
- CWE-674 - Uncontrolled Recursion
Assigner
References
2 references
| URL | Tags |
|---|---|
| https://github.com/nltk/nltk/security/advisories/… | vendor-advisory |
| https://www.vulncheck.com/advisories/nltk-before-… | third-party-advisory |
Impacted products
Date Public
2026-03-18 00:00
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CVE-2026-65915 (GCVE-0-2026-65915)
Vulnerability from cvelistv5 – Published: 2026-08-22 14:12 – Updated: 2026-08-24 19:20
VLAI
EPSS
VEX
Title
NLTK before 3.10.0 Arbitrary File Read via FileSystemPathPointer
Summary
NLTK versions before 3.10.0 contain a logic bug in FileSystemPathPointer.open() where the sandbox validation check compares a normalized path against itself, making the security check permanently inert. Attackers can pass file:// URLs to nltk.data.load() to read arbitrary files accessible to the process user, including credentials and configuration files.
Severity
SSVC
Exploitation: poc
Automatable: no
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-08-24 19:20 UTC
CWE
- CWE-284 - Improper Access Control
Assigner
References
2 references
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| https://github.com/nltk/nltk/security/advisories/… | vendor-advisory |
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Impacted products
Date Public
2026-08-07 00:00
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CVE-2026-63312 (GCVE-0-2026-63312)
Vulnerability from cvelistv5 – Published: 2026-08-22 14:12 – Updated: 2026-08-24 18:34
VLAI
EPSS
VEX
Title
NLTK StreamBackedCorpusView Bypasses pathsec.ENFORCE Arbitrary File Read
Summary
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Severity
SSVC
Exploitation: poc
Automatable: yes
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-08-24 18:34 UTC
CWE
- CWE-22 - Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
Assigner
References
2 references
| URL | Tags |
|---|---|
| https://github.com/nltk/nltk/security/advisories/… | vendor-advisory |
| https://www.vulncheck.com/advisories/nltk-streamb… | third-party-advisory |
Impacted products
Date Public
2026-08-07 00:00
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CVE-2026-63311 (GCVE-0-2026-63311)
Vulnerability from cvelistv5 – Published: 2026-08-22 14:12 – Updated: 2026-08-26 16:16
VLAI
EPSS
VEX
Title
NLTK before 3.10.0 SSRF via DNS Resolution Failure
Summary
NLTK before 3.10.0 (affected versions <= 3.9.4) contains a server-side request forgery (SSRF) vulnerability in the validate_network_url() function in nltk/pathsec.py. The _resolve_hostname() helper catches OSError and ValueError during socket.getaddrinfo() and returns an empty list; when DNS resolution fails, the validation loop executes no IP checks and the function fails open, allowing urlopen() to proceed without validation. An attacker who can trigger DNS resolution failures or use DNS rebinding can bypass SSRF protections and reach restricted network resources, including cloud metadata endpoints (e.g., 169.254.169.254).
Severity
5.3 (Medium)
SSVC
Exploitation: none
Automatable: yes
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-08-26 15:58 UTC
CWE
- CWE-918 - Server-Side Request Forgery (SSRF)
Assigner
References
2 references
| URL | Tags |
|---|---|
| https://github.com/nltk/nltk/security/advisories/… | vendor-advisory |
| https://www.vulncheck.com/advisories/nltk-before-… | third-party-advisory |
Impacted products
Date Public
2026-08-07 00:00
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CVE-2026-62388 (GCVE-0-2026-62388)
Vulnerability from cvelistv5 – Published: 2026-08-22 14:12 – Updated: 2026-08-29 11:47
VLAI
EPSS
VEX
Title
NLTK before 3.10.0 Insecure Default Configuration in pathsec.py
Summary
NLTK versions before 3.10.0 default to ENFORCE=False in pathsec.py, causing all security validation functions to emit warnings instead of raising exceptions. Attackers can bypass path traversal and pickle deserialization protections by exploiting the disabled security controls that are only active when manually enabled.
Severity
SSVC
Exploitation: poc
Automatable: yes
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-08-26 17:53 UTC
CWE
- CWE-1188 - Initialization of a Resource with an Insecure Default
Assigner
References
2 references
| URL | Tags |
|---|---|
| https://github.com/nltk/nltk/security/advisories/… | vendor-advisory |
| https://www.vulncheck.com/advisories/nltk-before-… | third-party-advisory |
Impacted products
Date Public
2026-08-07 00:00
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CVE-2026-62385 (GCVE-0-2026-62385)
Vulnerability from cvelistv5 – Published: 2026-08-22 14:12 – Updated: 2026-08-24 19:07
VLAI
EPSS
VEX
Title
NLTK 3.9.4 Path Traversal via FrameNet and NKJP Readers
Summary
NLTK versions before 3.10.0 contain a path traversal vulnerability in FramenetCorpusReader and NKJPCorpusReader that allows attackers to parse XML files outside the corpus root by supplying unsafe selectors or poisoned index state. Attackers can exploit frame_by_name, doc, lu, and header methods with crafted parameters to read arbitrary XML files accessible to the application.
Severity
SSVC
Exploitation: poc
Automatable: no
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-08-24 19:07 UTC
CWE
- CWE-73 - External Control of File Name or Path
Assigner
References
2 references
| URL | Tags |
|---|---|
| https://github.com/nltk/nltk/security/advisories/… | vendor-advisory |
| https://www.vulncheck.com/advisories/nltk-path-tr… | third-party-advisory |
Impacted products
Date Public
2026-08-07 00:00
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CVE-2026-62384 (GCVE-0-2026-62384)
Vulnerability from cvelistv5 – Published: 2026-08-22 14:12 – Updated: 2026-08-24 18:39
VLAI
EPSS
VEX
Title
NLTK FramenetCorpusReader Symlink Sandbox Bypass before 3.10.2
Summary
NLTK versions before 3.10.2 contain a symlink-based sandbox bypass in FramenetCorpusReader that allows attackers to read arbitrary XML files outside the corpus root. Attackers can place symlinks with names containing no path separators inside the corpus subdirectory, which pass the path validation guard and are resolved to files outside the intended corpus root when accessed via frame_by_name(), _lu_file(), or doc() methods.
Severity
SSVC
Exploitation: poc
Automatable: yes
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-08-24 18:39 UTC
CWE
- CWE-22 - Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
Assigner
References
2 references
| URL | Tags |
|---|---|
| https://github.com/nltk/nltk/security/advisories/… | vendor-advisory |
| https://www.vulncheck.com/advisories/nltk-framene… | third-party-advisory |
Impacted products
Date Public
2026-08-07 00:00
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CVE-2026-62383 (GCVE-0-2026-62383)
Vulnerability from cvelistv5 – Published: 2026-08-22 14:12 – Updated: 2026-08-26 16:16
VLAI
EPSS
VEX
Title
nltk IPIPANCorpusReader Symlink Arbitrary File Read
Summary
nltk versions before 3.10.2 contain a symlink-based arbitrary file read vulnerability in IPIPANCorpusReader methods that bypass nltk.pathsec validation entirely. Attackers can place a symlink in the corpus root directory and read arbitrary files accessible to the process by calling channels(), domains(), categories(), or fileids() methods with the symlink filename.
Severity
5.5 (Medium)
SSVC
Exploitation: none
Automatable: no
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-08-26 15:55 UTC
CWE
- CWE-22 - Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
Assigner
References
2 references
| URL | Tags |
|---|---|
| https://github.com/nltk/nltk/security/advisories/… | vendor-advisory |
| https://www.vulncheck.com/advisories/nltk-ipipanc… | third-party-advisory |
Impacted products
Date Public
2026-08-07 00:00
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CVE-2026-71514 (GCVE-0-2026-71514)
Vulnerability from cvelistv5 – Published: 2026-08-22 13:34 – Updated: 2026-08-24 19:18
VLAI
EPSS
VEX
Title
NLTK 3.9.4 through 3.10.2 Path Traversal via CrubadanCorpusReader pathsec Bypass
Summary
NLTK 3.9.4 through 3.10.2 contains a path traversal vulnerability in CrubadanCorpusReader. _load_lang_ngrams joins the corpus root with crubadan_code, the column-0 value read from the corpus table.txt mapping file, and opens the result with the builtin open() rather than the pathsec-validated opener, so os.path.join discards the root when that value is absolute and the read escapes the corpus directory without the containment check nltk.pathsec applies when ENFORCE is set. An attacker who controls a corpus package can disclose file contents outside the corpus root through lang_freq, limited to paths ending in -3grams.txt whose contents parse as token count lines.
Severity
SSVC
Exploitation: none
Automatable: no
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-08-24 19:17 UTC
CWE
- CWE-22 - Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
Assigner
References
4 references
| URL | Tags |
|---|---|
| https://github.com/nltk/nltk/commit/10d34b3f4fe3f… | patch |
| https://github.com/nltk/nltk | product |
| https://github.com/nltk/nltk/blob/v3.10.2/nltk/co… | technical-description |
| https://www.vulncheck.com/advisories/nltk-through… | third-party-advisory |
Impacted products
Date Public
2026-08-11 00:00
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CVE-2026-71513 (GCVE-0-2026-71513)
Vulnerability from cvelistv5 – Published: 2026-08-22 13:34 – Updated: 2026-08-27 16:24
VLAI
EPSS
VEX
Title
NLTK 3.10.0 through 3.10.2 Remote Code Execution via AllowlistUnpickler Dotted-Name Bypass
Summary
NLTK before 3.10.3 contains a remote code execution vulnerability in AllowlistUnpickler that validates only the pickle module string and not the global name, allowing attackers to resolve dotted names by attribute traversal to callables outside the allowlisted namespace. Attackers can craft untrusted transition-parser models that execute arbitrary commands when TransitionParser.parse loads the model through allowlisted_pickle_load.
Severity
SSVC
Exploitation: none
Automatable: no
Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-08-25 03:56 UTC
CWE
- CWE-502 - Deserialization of Untrusted Data
Assigner
References
4 references
| URL | Tags |
|---|---|
| https://github.com/nltk/nltk/commit/c3e37113742a1… | patch |
| https://github.com/nltk/nltk | product |
| https://github.com/nltk/nltk/blob/v3.10.2/nltk/pi… | technical-description |
| https://www.vulncheck.com/advisories/nltk-through… | third-party-advisory |
Impacted products
Date Public
2026-08-11 00:00
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CVE-2026-72818 (GCVE-0-2026-72818)
Vulnerability from cvelistv5 – Published: 2026-08-20 21:57 – Updated: 2026-09-24 14:18
VLAI
EPSS
VEX
Title
NLTK TweetTokenizer URL Pattern Backtracks Catastrophically on Naked-Domain-Like Input
Summary
The URLS regular expression in nltk/tokenize/casual.py, compiled into TweetTokenizer.WORD_RE and applied by TweetTokenizer.tokenize, contains a naked-domain branch whose domain-label prefix [a-z0-9]+(?:[.\-][a-z0-9]+)* is unbounded. Input consisting of many alternating label separators can be partitioned in exponentially many ways, and because the branch also requires a trailing top-level domain that such input never supplies, the engine explores those partitions before failing at each offset. A few kilobytes of input therefore consumes seconds to minutes of single-threaded CPU, and the HANG_RE substitution performed before matching does not collapse the pattern. TweetTokenizer is intended for tokenizing untrusted social-media text, so any service that applies it, or the module-level casual_tokenize, to submitted text can be stalled per request without authentication. Version 3.10.1 bounds the label repetition.
Severity
SSVC
Exploitation: poc
Automatable: yes
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-08-21 11:05 UTC
CWE
- CWE-1333 - Inefficient Regular Expression Complexity
Assigner
References
5 references
| URL | Tags |
|---|---|
| https://github.com/nltk/nltk/issues/3704 | issue-tracking |
| https://github.com/nltk/nltk/blob/3.9.4/nltk/toke… | technical-description |
| https://github.com/nltk/nltk/releases/tag/v3.10.1 | release-notes |
| https://github.com/nltk/nltk | product |
| https://www.vulncheck.com/advisories/nltk-tweetto… | third-party-advisory |
Impacted products
1 product
| Vendor | Product | Version | |
|---|---|---|---|
| nltk | nltk |
Affected:
0 , < 3.10.1
(semver)
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Date Public
2026-07-12 00:00
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CVE-2026-12372 (GCVE-0-2026-12372)
Vulnerability from cvelistv5 – Published: 2026-08-09 22:45 – Updated: 2026-08-12 17:48
VLAI
EPSS
VEX
Title
Server-Side Request Forgery (SSRF) in nltk/nltk
Summary
A Server-Side Request Forgery (SSRF) vulnerability exists in nltk/nltk versions 3.9.4 and the current develop branch. The `nltk.pathsec.validate_network_url()` function, intended to prevent SSRF by rejecting internal network addresses, fails to reject IPs in the RFC 6598 shared address space (`100.64.0.0/10`). This occurs because Python's `ipaddress` module does not classify such addresses as `is_private` or `is_global`, and the current guard only checks `is_private` and a few explicit categories. An attacker who can influence a URL passed to NLTK's network-loading helpers can exploit this vulnerability to make a strict-mode application send requests to shared-address-space hosts, potentially exposing non-public infrastructure reachable from the application host. The impact is limited to SSRF-style confidentiality exposure, with no code execution claimed.
Severity
SSVC
Exploitation: poc
Automatable: no
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-08-12 17:45 UTC
CWE
- CWE-918 - Server-Side Request Forgery (SSRF)
Assigner
References
1 reference
Impacted products
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CVE-2026-12261 (GCVE-0-2026-12261)
Vulnerability from cvelistv5 – Published: 2026-08-07 06:25 – Updated: 2026-08-07 15:27
VLAI
EPSS
VEX
Title
Improper Access Control in nltk/nltk
Summary
A vulnerability in `nltk.downloader` in nltk/nltk versions <= 3.9.4 allows for cross-package resource and model poisoning. The downloader extracts package archives into shared namespaces such as `corpora/` and `taggers/` instead of package-isolated roots, and validates package integrity only after the archive has been written and extracted. This design flaw enables one package to overwrite another package's trusted resources within the same namespace, making the changes immediately active through ordinary NLTK APIs. This issue persists across fresh interpreter restarts and can affect downstream workflows, including machine learning pipelines and reproducibility-sensitive environments.
Severity
5.3 (Medium)
SSVC
Exploitation: poc
Automatable: no
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-08-07 15:25 UTC
CWE
- CWE-284 - Improper Access Control
Assigner
References
1 reference
Impacted products
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