{
  "affected": [
    {
      "ecosystem_specific": {
        "fix": null,
        "range_state": "affected",
        "resource": "tornado",
        "resource_purl": "pkg:pypi/tornado@6.5.8",
        "upstream_fixed_in": "6.5.9"
      },
      "package": {
        "ecosystem": "Homebrew",
        "name": "livereload",
        "purl": "pkg:brew/livereload"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2.7.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "database_specific": {
    "confidence": "high",
    "source": "matched",
    "strategy": "registry",
    "upstream_evidence": [
      {
        "ecosystem": "PyPI",
        "key": "pkg:pypi/tornado@6.5.8",
        "name": "tornado",
        "resource": "tornado",
        "strategy": "registry",
        "subject_version": "6.5.8"
      }
    ]
  },
  "details": "## Summary\n\n`HTTPServerRequest.__init__` in `tornado/httputil.py` parses the URL query string via\n`parse_qs_bytes()` with no field-count limit \u2014 while the sibling POST-body parsing path\n(`parse_body_arguments`) received a `max_num_fields=1000` cap added earlier in this exact\nsame release (v6.5.8, commit `8d6363ed`), explicitly to bound parsing cost for the identical\nunderlying primitive. This leaves the query-string path with the resource-exhaustion exposure\nthe body-path fix was meant to close.\n\n**File**: `tornado/httputil.py`, line 553 (`HTTPServerRequest.__init__`)\n\n### Root Cause\n\n```python\n# tornado/httputil.py:553 (before fix)\nself.arguments = parse_qs_bytes(self.query, keep_blank_values=True)\n```\n\nCompare with the POST-body path fixed one commit earlier in the same release:\n\n```python\n# tornado/httputil.py:1038-1041\nuri_arguments = parse_qs_bytes(\n    body,\n    keep_blank_values=True,\n    max_num_fields=config.urlencoded.max_arguments,  # default 1000\n)\n```\n\nBoth call sites funnel through the same `tornado.escape.parse_qs_bytes` (a thin wrapper over\n`urllib.parse.parse_qs`), which is exactly why `max_num_fields` was added to\n`urllib.parse.parse_qsl` upstream \u2014 to let frameworks bound field count. The fix was applied\nonly to the body path; the query-string path was missed.\n\nThe request line + headers together are capped at `max_header_size` (default 65536 bytes), so\nthis is not literally unbounded, but a single ~64KB request line can carry thousands of short\n`key=value` pairs \u2014 far beyond the 1000-field limit the maintainer judged appropriate for the\nstructurally identical body case.\n\n### Attack Scenario\n\n1. Attacker sends a `GET` request whose query string is packed with thousands of short fields\n   (e.g. `k0=1\u0026k1=1\u0026...\u0026k7799=1`, ~61KB), fitting comfortably under `max_header_size`. No\n   authentication, cookies, or prior state required.\n2. Tornado accepts and parses this with no field-count cap, unlike the equivalent POST-body\n   request (which is correctly rejected with 400 once \u003e1000 fields are present).\n3. Parsing thousands of fields is CPU work performed synchronously inside Tornado\u0027s\n   single-threaded `IOLoop`. Several such requests in flight concurrently stall the event\n   loop, delaying processing of *all* other connections on that loop \u2014 not just the\n   attacker\u0027s own request.\n\n### Verification (dynamic, local reproduction against v6.5.8)\n\nRan the unmodified v6.5.8 source directly (no external dependencies needed) with a minimal\n`tornado.web.Application` on `127.0.0.1:8888`.\n\n- Identical 7800-field/~61KB payload sent as GET query string \u2192 `200 OK`; sent as POST body\n  (`application/x-www-form-urlencoded`) \u2192 `400 Bad Request` (correctly rejected by the\n  existing `max_num_fields` body-path limit). This confirms the asymmetry directly.\n- Per-request parse cost: baseline (`/?a=1`) averaged 1.86ms; the 7800-field query string\n  averaged 25.1ms (~13x).\n- Event-loop-blocking amplification (raw-socket test, isolating server-side stall from\n  client overhead): with 10 sequential baseline probe requests fired with no load, average\n  latency was 1.47ms (max 5.9ms). With 5 concurrent 61KB/7800-field requests in flight,\n  the same baseline probes averaged 13.0ms (max 118.1ms) \u2014 an **8.9x average slowdown** for\n  unrelated clients, produced by ~305KB of unauthenticated attacker traffic.\n\n### Impact\n\nAll Tornado servers/applications are affected \u2014 this triggers on every request with a query\nstring, independent of application/handler logic. An unauthenticated, unprivileged remote\nattacker can measurably degrade response times for all other clients sharing the same\n`IOLoop`, using a small amount of bandwidth and no special conditions. This is an\navailability/DoS concern; no confidentiality or integrity impact.\n\n### Recommended Fix\n\n```python\n# tornado/httputil.py \u2014 HTTPServerRequest.__init__\nif uri is not None:\n    self.path, sep, self.query = uri.partition(\"?\")\ntry:\n    self.arguments = parse_qs_bytes(\n        self.query,\n        keep_blank_values=True,\n        max_num_fields=_DEFAULT_PARSE_BODY_CONFIG.urlencoded.max_arguments,\n    )\nexcept ValueError as e:\n    raise HTTPInputError(\"Invalid query string: %s\" % e) from e\n```\n\nThis reuses the existing `ParseUrlEncodedConfig.max_arguments` default (1000) via the\nmodule\u0027s `_DEFAULT_PARSE_BODY_CONFIG`, matching the POST-body limit and honoring any global\noverride via `set_parse_body_config()`. The `try/except` is necessary because \u2014 unlike\n`parse_body_arguments`, which already wraps its call and converts `ValueError` into a clean\n`HTTPInputError`/400 \u2014 the query-string call site currently has no such handling, so without\nit, a request exceeding the limit would raise an uncaught `ValueError` instead of a clean 400.\n\nVerified: with the fix applied, requests with \u22641000 query-string fields are unaffected;\nrequests with \u003e1000 fields are rejected with `400 Bad Request` (consistent with the POST-body\nbehavior); Tornado\u0027s own `httputil_test` and `web_test` suites (256 tests) pass unchanged.",
  "id": "BREW-livereload-GHSA-3hv7-mjh2-fv65",
  "modified": "2026-10-02T10:51:52Z",
  "published": "2026-10-01T11:13:05Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/tornadoweb/tornado/security/advisories/GHSA-3hv7-mjh2-fv65"
    },
    {
      "type": "WEB",
      "url": "https://github.com/tornadoweb/tornado/pull/3719"
    },
    {
      "type": "WEB",
      "url": "https://github.com/tornadoweb/tornado/commit/03945136ea9746eccf61caf88edae39642e59c93"
    },
    {
      "type": "WEB",
      "url": "https://github.com/tornadoweb/tornado/commit/8a61dd6005f42733015160f3c23a2bcffe200542"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/tornadoweb/tornado"
    },
    {
      "type": "WEB",
      "url": "https://github.com/tornadoweb/tornado/releases/tag/v6.5.9"
    }
  ],
  "schema_version": "1.7.3",
  "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": "Tornado: Unbounded query-string argument count allows event-loop-stalling DoS",
  "upstream": [
    "GHSA-3hv7-mjh2-fv65",
    "CVE-2026-103261"
  ]
}

{
  "affected": [
    {
      "ecosystem_specific": {
        "fix": null,
        "range_state": "affected",
        "resource": "tornado",
        "resource_purl": "pkg:pypi/tornado@6.5.8",
        "upstream_fixed_in": "6.5.9"
      },
      "package": {
        "ecosystem": "Homebrew",
        "name": "nvchecker",
        "purl": "pkg:brew/nvchecker"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2.7"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "database_specific": {
    "confidence": "high",
    "source": "matched",
    "strategy": "registry",
    "upstream_evidence": [
      {
        "ecosystem": "PyPI",
        "key": "pkg:pypi/tornado@6.5.8",
        "name": "tornado",
        "resource": "tornado",
        "strategy": "registry",
        "subject_version": "6.5.8"
      }
    ]
  },
  "details": "## Summary\n\n`HTTPServerRequest.__init__` in `tornado/httputil.py` parses the URL query string via\n`parse_qs_bytes()` with no field-count limit \u2014 while the sibling POST-body parsing path\n(`parse_body_arguments`) received a `max_num_fields=1000` cap added earlier in this exact\nsame release (v6.5.8, commit `8d6363ed`), explicitly to bound parsing cost for the identical\nunderlying primitive. This leaves the query-string path with the resource-exhaustion exposure\nthe body-path fix was meant to close.\n\n**File**: `tornado/httputil.py`, line 553 (`HTTPServerRequest.__init__`)\n\n### Root Cause\n\n```python\n# tornado/httputil.py:553 (before fix)\nself.arguments = parse_qs_bytes(self.query, keep_blank_values=True)\n```\n\nCompare with the POST-body path fixed one commit earlier in the same release:\n\n```python\n# tornado/httputil.py:1038-1041\nuri_arguments = parse_qs_bytes(\n    body,\n    keep_blank_values=True,\n    max_num_fields=config.urlencoded.max_arguments,  # default 1000\n)\n```\n\nBoth call sites funnel through the same `tornado.escape.parse_qs_bytes` (a thin wrapper over\n`urllib.parse.parse_qs`), which is exactly why `max_num_fields` was added to\n`urllib.parse.parse_qsl` upstream \u2014 to let frameworks bound field count. The fix was applied\nonly to the body path; the query-string path was missed.\n\nThe request line + headers together are capped at `max_header_size` (default 65536 bytes), so\nthis is not literally unbounded, but a single ~64KB request line can carry thousands of short\n`key=value` pairs \u2014 far beyond the 1000-field limit the maintainer judged appropriate for the\nstructurally identical body case.\n\n### Attack Scenario\n\n1. Attacker sends a `GET` request whose query string is packed with thousands of short fields\n   (e.g. `k0=1\u0026k1=1\u0026...\u0026k7799=1`, ~61KB), fitting comfortably under `max_header_size`. No\n   authentication, cookies, or prior state required.\n2. Tornado accepts and parses this with no field-count cap, unlike the equivalent POST-body\n   request (which is correctly rejected with 400 once \u003e1000 fields are present).\n3. Parsing thousands of fields is CPU work performed synchronously inside Tornado\u0027s\n   single-threaded `IOLoop`. Several such requests in flight concurrently stall the event\n   loop, delaying processing of *all* other connections on that loop \u2014 not just the\n   attacker\u0027s own request.\n\n### Verification (dynamic, local reproduction against v6.5.8)\n\nRan the unmodified v6.5.8 source directly (no external dependencies needed) with a minimal\n`tornado.web.Application` on `127.0.0.1:8888`.\n\n- Identical 7800-field/~61KB payload sent as GET query string \u2192 `200 OK`; sent as POST body\n  (`application/x-www-form-urlencoded`) \u2192 `400 Bad Request` (correctly rejected by the\n  existing `max_num_fields` body-path limit). This confirms the asymmetry directly.\n- Per-request parse cost: baseline (`/?a=1`) averaged 1.86ms; the 7800-field query string\n  averaged 25.1ms (~13x).\n- Event-loop-blocking amplification (raw-socket test, isolating server-side stall from\n  client overhead): with 10 sequential baseline probe requests fired with no load, average\n  latency was 1.47ms (max 5.9ms). With 5 concurrent 61KB/7800-field requests in flight,\n  the same baseline probes averaged 13.0ms (max 118.1ms) \u2014 an **8.9x average slowdown** for\n  unrelated clients, produced by ~305KB of unauthenticated attacker traffic.\n\n### Impact\n\nAll Tornado servers/applications are affected \u2014 this triggers on every request with a query\nstring, independent of application/handler logic. An unauthenticated, unprivileged remote\nattacker can measurably degrade response times for all other clients sharing the same\n`IOLoop`, using a small amount of bandwidth and no special conditions. This is an\navailability/DoS concern; no confidentiality or integrity impact.\n\n### Recommended Fix\n\n```python\n# tornado/httputil.py \u2014 HTTPServerRequest.__init__\nif uri is not None:\n    self.path, sep, self.query = uri.partition(\"?\")\ntry:\n    self.arguments = parse_qs_bytes(\n        self.query,\n        keep_blank_values=True,\n        max_num_fields=_DEFAULT_PARSE_BODY_CONFIG.urlencoded.max_arguments,\n    )\nexcept ValueError as e:\n    raise HTTPInputError(\"Invalid query string: %s\" % e) from e\n```\n\nThis reuses the existing `ParseUrlEncodedConfig.max_arguments` default (1000) via the\nmodule\u0027s `_DEFAULT_PARSE_BODY_CONFIG`, matching the POST-body limit and honoring any global\noverride via `set_parse_body_config()`. The `try/except` is necessary because \u2014 unlike\n`parse_body_arguments`, which already wraps its call and converts `ValueError` into a clean\n`HTTPInputError`/400 \u2014 the query-string call site currently has no such handling, so without\nit, a request exceeding the limit would raise an uncaught `ValueError` instead of a clean 400.\n\nVerified: with the fix applied, requests with \u22641000 query-string fields are unaffected;\nrequests with \u003e1000 fields are rejected with `400 Bad Request` (consistent with the POST-body\nbehavior); Tornado\u0027s own `httputil_test` and `web_test` suites (256 tests) pass unchanged.",
  "id": "BREW-nvchecker-GHSA-3hv7-mjh2-fv65",
  "modified": "2026-10-02T09:20:08Z",
  "published": "2026-10-01T09:49:09Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/tornadoweb/tornado/security/advisories/GHSA-3hv7-mjh2-fv65"
    },
    {
      "type": "WEB",
      "url": "https://github.com/tornadoweb/tornado/pull/3719"
    },
    {
      "type": "WEB",
      "url": "https://github.com/tornadoweb/tornado/commit/03945136ea9746eccf61caf88edae39642e59c93"
    },
    {
      "type": "WEB",
      "url": "https://github.com/tornadoweb/tornado/commit/8a61dd6005f42733015160f3c23a2bcffe200542"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/tornadoweb/tornado"
    },
    {
      "type": "WEB",
      "url": "https://github.com/tornadoweb/tornado/releases/tag/v6.5.9"
    }
  ],
  "schema_version": "1.7.3",
  "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": "Tornado: Unbounded query-string argument count allows event-loop-stalling DoS",
  "upstream": [
    "GHSA-3hv7-mjh2-fv65",
    "CVE-2026-103261"
  ]
}

{
  "affected": [
    {
      "ecosystem_specific": {
        "fix": "bump",
        "range_state": "fixed",
        "resource": "tornado",
        "resource_purl": "pkg:pypi/tornado@6.5.10",
        "upstream_fixed_in": "6.5.9"
      },
      "package": {
        "ecosystem": "Homebrew",
        "name": "sickchill",
        "purl": "pkg:brew/sickchill"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2023.5.30"
            },
            {
              "fixed": "2024.3.1_9"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "database_specific": {
    "confidence": "high",
    "source": "matched",
    "strategy": "registry",
    "upstream_evidence": [
      {
        "ecosystem": "PyPI",
        "key": "pkg:pypi/tornado@6.5.10",
        "name": "tornado",
        "resource": "tornado",
        "strategy": "registry",
        "subject_version": "6.5.10"
      }
    ]
  },
  "details": "## Summary\n\n`HTTPServerRequest.__init__` in `tornado/httputil.py` parses the URL query string via\n`parse_qs_bytes()` with no field-count limit \u2014 while the sibling POST-body parsing path\n(`parse_body_arguments`) received a `max_num_fields=1000` cap added earlier in this exact\nsame release (v6.5.8, commit `8d6363ed`), explicitly to bound parsing cost for the identical\nunderlying primitive. This leaves the query-string path with the resource-exhaustion exposure\nthe body-path fix was meant to close.\n\n**File**: `tornado/httputil.py`, line 553 (`HTTPServerRequest.__init__`)\n\n### Root Cause\n\n```python\n# tornado/httputil.py:553 (before fix)\nself.arguments = parse_qs_bytes(self.query, keep_blank_values=True)\n```\n\nCompare with the POST-body path fixed one commit earlier in the same release:\n\n```python\n# tornado/httputil.py:1038-1041\nuri_arguments = parse_qs_bytes(\n    body,\n    keep_blank_values=True,\n    max_num_fields=config.urlencoded.max_arguments,  # default 1000\n)\n```\n\nBoth call sites funnel through the same `tornado.escape.parse_qs_bytes` (a thin wrapper over\n`urllib.parse.parse_qs`), which is exactly why `max_num_fields` was added to\n`urllib.parse.parse_qsl` upstream \u2014 to let frameworks bound field count. The fix was applied\nonly to the body path; the query-string path was missed.\n\nThe request line + headers together are capped at `max_header_size` (default 65536 bytes), so\nthis is not literally unbounded, but a single ~64KB request line can carry thousands of short\n`key=value` pairs \u2014 far beyond the 1000-field limit the maintainer judged appropriate for the\nstructurally identical body case.\n\n### Attack Scenario\n\n1. Attacker sends a `GET` request whose query string is packed with thousands of short fields\n   (e.g. `k0=1\u0026k1=1\u0026...\u0026k7799=1`, ~61KB), fitting comfortably under `max_header_size`. No\n   authentication, cookies, or prior state required.\n2. Tornado accepts and parses this with no field-count cap, unlike the equivalent POST-body\n   request (which is correctly rejected with 400 once \u003e1000 fields are present).\n3. Parsing thousands of fields is CPU work performed synchronously inside Tornado\u0027s\n   single-threaded `IOLoop`. Several such requests in flight concurrently stall the event\n   loop, delaying processing of *all* other connections on that loop \u2014 not just the\n   attacker\u0027s own request.\n\n### Verification (dynamic, local reproduction against v6.5.8)\n\nRan the unmodified v6.5.8 source directly (no external dependencies needed) with a minimal\n`tornado.web.Application` on `127.0.0.1:8888`.\n\n- Identical 7800-field/~61KB payload sent as GET query string \u2192 `200 OK`; sent as POST body\n  (`application/x-www-form-urlencoded`) \u2192 `400 Bad Request` (correctly rejected by the\n  existing `max_num_fields` body-path limit). This confirms the asymmetry directly.\n- Per-request parse cost: baseline (`/?a=1`) averaged 1.86ms; the 7800-field query string\n  averaged 25.1ms (~13x).\n- Event-loop-blocking amplification (raw-socket test, isolating server-side stall from\n  client overhead): with 10 sequential baseline probe requests fired with no load, average\n  latency was 1.47ms (max 5.9ms). With 5 concurrent 61KB/7800-field requests in flight,\n  the same baseline probes averaged 13.0ms (max 118.1ms) \u2014 an **8.9x average slowdown** for\n  unrelated clients, produced by ~305KB of unauthenticated attacker traffic.\n\n### Impact\n\nAll Tornado servers/applications are affected \u2014 this triggers on every request with a query\nstring, independent of application/handler logic. An unauthenticated, unprivileged remote\nattacker can measurably degrade response times for all other clients sharing the same\n`IOLoop`, using a small amount of bandwidth and no special conditions. This is an\navailability/DoS concern; no confidentiality or integrity impact.\n\n### Recommended Fix\n\n```python\n# tornado/httputil.py \u2014 HTTPServerRequest.__init__\nif uri is not None:\n    self.path, sep, self.query = uri.partition(\"?\")\ntry:\n    self.arguments = parse_qs_bytes(\n        self.query,\n        keep_blank_values=True,\n        max_num_fields=_DEFAULT_PARSE_BODY_CONFIG.urlencoded.max_arguments,\n    )\nexcept ValueError as e:\n    raise HTTPInputError(\"Invalid query string: %s\" % e) from e\n```\n\nThis reuses the existing `ParseUrlEncodedConfig.max_arguments` default (1000) via the\nmodule\u0027s `_DEFAULT_PARSE_BODY_CONFIG`, matching the POST-body limit and honoring any global\noverride via `set_parse_body_config()`. The `try/except` is necessary because \u2014 unlike\n`parse_body_arguments`, which already wraps its call and converts `ValueError` into a clean\n`HTTPInputError`/400 \u2014 the query-string call site currently has no such handling, so without\nit, a request exceeding the limit would raise an uncaught `ValueError` instead of a clean 400.\n\nVerified: with the fix applied, requests with \u22641000 query-string fields are unaffected;\nrequests with \u003e1000 fields are rejected with `400 Bad Request` (consistent with the POST-body\nbehavior); Tornado\u0027s own `httputil_test` and `web_test` suites (256 tests) pass unchanged.",
  "id": "BREW-sickchill-GHSA-3hv7-mjh2-fv65",
  "modified": "2026-10-02T09:24:45Z",
  "published": "2026-10-01T09:53:21Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/tornadoweb/tornado/security/advisories/GHSA-3hv7-mjh2-fv65"
    },
    {
      "type": "WEB",
      "url": "https://github.com/tornadoweb/tornado/pull/3719"
    },
    {
      "type": "WEB",
      "url": "https://github.com/tornadoweb/tornado/commit/03945136ea9746eccf61caf88edae39642e59c93"
    },
    {
      "type": "WEB",
      "url": "https://github.com/tornadoweb/tornado/commit/8a61dd6005f42733015160f3c23a2bcffe200542"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/tornadoweb/tornado"
    },
    {
      "type": "WEB",
      "url": "https://github.com/tornadoweb/tornado/releases/tag/v6.5.9"
    }
  ],
  "schema_version": "1.7.3",
  "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": "Tornado: Unbounded query-string argument count allows event-loop-stalling DoS",
  "upstream": [
    "GHSA-3hv7-mjh2-fv65",
    "CVE-2026-103261"
  ]
}

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "packageURL": "pkg:pypi/tornado",
          "product": "tornado",
          "vendor": "tornadoweb",
          "versions": [
            {
              "lessThan": "6.5.9",
              "status": "affected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "status": "unaffected",
              "version": "6.5.9",
              "versionType": "semver"
            }
          ]
        }
      ],
      "source": "disclosure@vulncheck.com"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "Tornado before 6.5.9 fails to limit the number of query string fields in HTTPServerRequest.__init__, allowing remote attackers to cause event-loop stalling by sending requests with thousands of query parameters. Attackers can send unauthenticated GET requests with unbounded query-string field counts to degrade response times for all clients sharing the same IOLoop."
    }
  ],
  "id": "CVE-2026-103261",
  "lastModified": "2026-10-01T15:17:26.580",
  "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": "disclosure@vulncheck.com",
        "type": "Secondary"
      }
    ],
    "cvssMetricV40": [
      {
        "cvssData": {
          "Automatable": "NOT_DEFINED",
          "Recovery": "NOT_DEFINED",
          "Safety": "NOT_DEFINED",
          "attackComplexity": "LOW",
          "attackRequirements": "NONE",
          "attackVector": "NETWORK",
          "availabilityRequirement": "NOT_DEFINED",
          "baseScore": 6.9,
          "baseSeverity": "MEDIUM",
          "confidentialityRequirement": "NOT_DEFINED",
          "exploitMaturity": "NOT_DEFINED",
          "integrityRequirement": "NOT_DEFINED",
          "modifiedAttackComplexity": "NOT_DEFINED",
          "modifiedAttackRequirements": "NOT_DEFINED",
          "modifiedAttackVector": "NOT_DEFINED",
          "modifiedPrivilegesRequired": "NOT_DEFINED",
          "modifiedSubAvailabilityImpact": "NOT_DEFINED",
          "modifiedSubConfidentialityImpact": "NOT_DEFINED",
          "modifiedSubIntegrityImpact": "NOT_DEFINED",
          "modifiedUserInteraction": "NOT_DEFINED",
          "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
          "modifiedVulnConfidentialityImpact": "NOT_DEFINED",
          "modifiedVulnIntegrityImpact": "NOT_DEFINED",
          "privilegesRequired": "NONE",
          "providerUrgency": "NOT_DEFINED",
          "subAvailabilityImpact": "NONE",
          "subConfidentialityImpact": "NONE",
          "subIntegrityImpact": "NONE",
          "userInteraction": "NONE",
          "valueDensity": "NOT_DEFINED",
          "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
          "version": "4.0",
          "vulnAvailabilityImpact": "LOW",
          "vulnConfidentialityImpact": "NONE",
          "vulnIntegrityImpact": "NONE",
          "vulnerabilityResponseEffort": "NOT_DEFINED"
        },
        "source": "disclosure@vulncheck.com",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-103261",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "yes"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-10-01T14:44:15.608259Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-10-01T11:17:20.847",
  "references": [
    {
      "source": "disclosure@vulncheck.com",
      "url": "https://github.com/tornadoweb/tornado/commit/03945136ea9746eccf61caf88edae39642e59c93"
    },
    {
      "source": "disclosure@vulncheck.com",
      "url": "https://github.com/tornadoweb/tornado/security/advisories/GHSA-3hv7-mjh2-fv65"
    },
    {
      "source": "disclosure@vulncheck.com",
      "url": "https://www.vulncheck.com/advisories/tornado-before-6.5.9-denial-of-service-via-query-string"
    }
  ],
  "sourceIdentifier": "disclosure@vulncheck.com",
  "vulnStatus": "Deferred",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-770"
        }
      ],
      "source": "disclosure@vulncheck.com",
      "type": "Secondary"
    }
  ]
}

{
  "affected": [],
  "aliases": [
    "CVE-2026-103261"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-770"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-10-01T11:17:20Z",
    "severity": "MODERATE"
  },
  "details": "Tornado before 6.5.9 fails to limit the number of query string fields in HTTPServerRequest.__init__, allowing remote attackers to cause event-loop stalling by sending requests with thousands of query parameters. Attackers can send unauthenticated GET requests with unbounded query-string field counts to degrade response times for all clients sharing the same IOLoop.",
  "id": "GHSA-2v9w-f3h6-74rj",
  "modified": "2026-10-01T12:31:16Z",
  "published": "2026-10-01T12:31:16Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/tornadoweb/tornado/security/advisories/GHSA-3hv7-mjh2-fv65"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-103261"
    },
    {
      "type": "WEB",
      "url": "https://github.com/tornadoweb/tornado/commit/03945136ea9746eccf61caf88edae39642e59c93"
    },
    {
      "type": "WEB",
      "url": "https://www.vulncheck.com/advisories/tornado-before-6.5.9-denial-of-service-via-query-string"
    }
  ],
  "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"
    },
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
      "type": "CVSS_V4"
    }
  ]
}

{
  "affected": [
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "python-tornado",
            "binary_version": "4.2.1-1ubuntu3.1+esm3"
          },
          {
            "binary_name": "python3-tornado",
            "binary_version": "4.2.1-1ubuntu3.1+esm3"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:16.04:LTS",
        "name": "python-tornado",
        "purl": "pkg:deb/ubuntu/python-tornado@4.2.1-1ubuntu3.1+esm3?arch=source\u0026distro=esm-infra/xenial"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "4.2.1-1ubuntu2",
        "4.2.1-1ubuntu3",
        "4.2.1-1ubuntu3.1",
        "4.2.1-1ubuntu3.1+esm1",
        "4.2.1-1ubuntu3.1+esm2",
        "4.2.1-1ubuntu3.1+esm3"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "python-tornado",
            "binary_version": "4.5.3-1ubuntu0.2+esm3"
          },
          {
            "binary_name": "python3-tornado",
            "binary_version": "4.5.3-1ubuntu0.2+esm3"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:18.04:LTS",
        "name": "python-tornado",
        "purl": "pkg:deb/ubuntu/python-tornado@4.5.3-1ubuntu0.2+esm3?arch=source\u0026distro=esm-apps/bionic"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "4.5.1-2.1~build2",
        "4.5.2-1",
        "4.5.3-1",
        "4.5.3-1ubuntu0.1",
        "4.5.3-1ubuntu0.2",
        "4.5.3-1ubuntu0.2+esm1",
        "4.5.3-1ubuntu0.2+esm2",
        "4.5.3-1ubuntu0.2+esm3"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "python3-tornado",
            "binary_version": "6.0.3+really5.1.1-3ubuntu0.1~esm5"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:20.04:LTS",
        "name": "python-tornado",
        "purl": "pkg:deb/ubuntu/python-tornado@6.0.3+really5.1.1-3ubuntu0.1~esm5?arch=source\u0026distro=esm-apps/focal"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "5.1.1-4ubuntu1",
        "5.1.1-4ubuntu5",
        "6.0.3+really5.1.1-2",
        "6.0.3+really5.1.1-2build1",
        "6.0.3+really5.1.1-2build2",
        "6.0.3+really5.1.1-3",
        "6.0.3+really5.1.1-3ubuntu0.1~esm1",
        "6.0.3+really5.1.1-3ubuntu0.1~esm3",
        "6.0.3+really5.1.1-3ubuntu0.1~esm5"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "python3-tornado",
            "binary_version": "6.1.0-3ubuntu0.1~esm5"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:22.04:LTS",
        "name": "python-tornado",
        "purl": "pkg:deb/ubuntu/python-tornado@6.1.0-3ubuntu0.1~esm5?arch=source\u0026distro=esm-apps/jammy"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
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      "versions": [
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        "6.1.0-2",
        "6.1.0-3",
        "6.1.0-3build1",
        "6.1.0-3ubuntu0.1~esm1",
        "6.1.0-3ubuntu0.1~esm2",
        "6.1.0-3ubuntu0.1~esm4",
        "6.1.0-3ubuntu0.1~esm5"
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    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "python3-tornado",
            "binary_version": "6.4.0-1ubuntu0.5"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:24.04:LTS",
        "name": "python-tornado",
        "purl": "pkg:deb/ubuntu/python-tornado@6.4.0-1ubuntu0.5?arch=source\u0026distro=noble"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "6.3.2-1",
        "6.4.0-0ubuntu1",
        "6.4.0-1",
        "6.4.0-1build1",
        "6.4.0-1ubuntu0.1",
        "6.4.0-1ubuntu0.2",
        "6.4.0-1ubuntu0.4",
        "6.4.0-1ubuntu0.5"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "python3-tornado",
            "binary_version": "6.5.4-0.1ubuntu0.1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:26.04:LTS",
        "name": "python-tornado",
        "purl": "pkg:deb/ubuntu/python-tornado@6.5.4-0.1ubuntu0.1?arch=source\u0026distro=resolute"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "6.4.2-3",
        "6.5.2-3",
        "6.5.4-0.1",
        "6.5.4-0.1ubuntu0.1"
      ]
    }
  ],
  "aliases": [],
  "details": "Tornado before 6.5.9 fails to limit the number of query string fields in HTTPServerRequest.__init__, allowing remote attackers to cause event-loop stalling by sending requests with thousands of query parameters. Attackers can send unauthenticated GET requests with unbounded query-string field counts to degrade response times for all clients sharing the same IOLoop.",
  "id": "UBUNTU-CVE-2026-103261",
  "modified": "2026-10-02T00:00:00Z",
  "published": "2026-10-02T00:00:00Z",
  "references": [
    {
      "type": "REPORT",
      "url": "https://ubuntu.com/security/CVE-2026-103261"
    },
    {
      "type": "REPORT",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-103261"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/tornadoweb/tornado/security/advisories/GHSA-3hv7-mjh2-fv65"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/tornadoweb/tornado/commit/03945136ea9746eccf61caf88edae39642e59c93"
    },
    {
      "type": "REPORT",
      "url": "https://www.vulncheck.com/advisories/tornado-before-6.5.9-denial-of-service-via-query-string"
    }
  ],
  "related": [],
  "schema_version": "1.7.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L",
      "type": "CVSS_V3"
    },
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    },
    {
      "score": "medium",
      "type": "Ubuntu"
    }
  ],
  "upstream": [
    "CVE-2026-103261"
  ]
}