GHSA-2V3C-QXHR-7VPV

Vulnerability from github – Published: 2026-10-27 19:01 – Updated: 2026-10-27 19:01
VLAI
Summary
Symfony: Unbounded Recursion in the YAML Inline Lexer Lets a Single Document Crash the Process
Details

Description

Yaml\Parser::lexInlineStructure() recursed through lexInlineMapping() and lexInlineSequence() for every { and [ of an inline collection, without entering the nesting level that the rest of the parser bounds with maxNestingLevel. A document made of deeply nested inline collections, such as [[[[...]]]], exhausted the stack while it was being lexed: depending on the PHP version and its stack settings, the process crashed or the request ended with a fatal error.

Any code parsing untrusted YAML is affected. That includes #[MapRequestPayload] when the Yaml component is installed and the endpoint does not restrict acceptFormat: a single unauthenticated request with a YAML content type is enough.

Resolution

The inline lexer now enters and leaves the same nesting level as the rest of the parser, so nested inline collections are bounded by maxNestingLevel, and the parser raises a ParseException beyond it.

The patches for this issue are available here for branch 5.4 (and forward-ported to 6.4, 7.4, 8.1 and 8.2).

Credits

We would like to thank Nicolas Grekas for reporting the issue and providing the fix.

References

Severity
8.7 (High)
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
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{
  "affected": [
    {
      "package": {
        "ecosystem": "Packagist",
        "name": "symfony/symfony"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2.0.0"
            },
            {
              "fixed": "5.4.54"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Packagist",
        "name": "symfony/symfony"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "6.0.0"
            },
            {
              "fixed": "6.4.45"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Packagist",
        "name": "symfony/symfony"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "7.0.0"
            },
            {
              "fixed": "7.4.18"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Packagist",
        "name": "symfony/symfony"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "8.0.0"
            },
            {
              "fixed": "8.1.6"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Packagist",
        "name": "symfony/yaml"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2.0.0"
            },
            {
              "fixed": "5.4.54"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Packagist",
        "name": "symfony/yaml"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "6.0.0"
            },
            {
              "fixed": "6.4.45"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Packagist",
        "name": "symfony/yaml"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "7.0.0"
            },
            {
              "fixed": "7.4.18"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Packagist",
        "name": "symfony/yaml"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "8.0.0"
            },
            {
              "fixed": "8.1.6"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-109413"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-674"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-10-27T19:01:50Z",
    "nvd_published_at": "2026-10-15T15:17:24Z",
    "severity": "HIGH"
  },
  "details": "### Description\n\n`Yaml\\Parser::lexInlineStructure()` recursed through `lexInlineMapping()` and `lexInlineSequence()` for every `{` and `[` of an inline collection, without entering the nesting level that the rest of the parser bounds with `maxNestingLevel`. A document made of deeply nested inline collections, such as `[[[[...]]]]`, exhausted the stack while it was being lexed: depending on the PHP version and its stack settings, the process crashed or the request ended with a fatal error.\n\nAny code parsing untrusted YAML is affected. That includes `#[MapRequestPayload]` when the Yaml component is installed and the endpoint does not restrict `acceptFormat`: a single unauthenticated request with a YAML content type is enough.\n\n### Resolution\n\nThe inline lexer now enters and leaves the same nesting level as the rest of the parser, so nested inline collections are bounded by `maxNestingLevel`, and the parser raises a `ParseException` beyond it.\n\nThe patches for this issue are available [here](https://github.com/symfony/symfony/commit/2a8bf9c58d862b0c76a35ce288d1ba6a27223aad) for branch 5.4 (and forward-ported to 6.4, 7.4, 8.1 and 8.2).\n\n### Credits\n\nWe would like to thank Nicolas Grekas for reporting the issue and providing the fix.\n\n### References\n\n- Fix: [#65688](https://github.com/symfony/symfony/pull/65688)",
  "id": "GHSA-2v3c-qxhr-7vpv",
  "modified": "2026-10-27T19:01:51Z",
  "published": "2026-10-27T19:01:50Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/symfony/symfony/security/advisories/GHSA-2v3c-qxhr-7vpv"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-109413"
    },
    {
      "type": "WEB",
      "url": "https://github.com/symfony/symfony/pull/65688"
    },
    {
      "type": "WEB",
      "url": "https://github.com/symfony/symfony/commit/116287c3b5bc057e7a0420d2e52d384e14ea9417"
    },
    {
      "type": "WEB",
      "url": "https://github.com/symfony/symfony/commit/2a8bf9c58d862b0c76a35ce288d1ba6a27223aad"
    },
    {
      "type": "WEB",
      "url": "https://github.com/symfony/symfony/commit/8fb436fed9658a79d220e9f2b1ba8a2095559018"
    },
    {
      "type": "WEB",
      "url": "https://github.com/symfony/symfony/commit/ab61e6cfd35042f16840a00f485eab2481dd4c2a"
    },
    {
      "type": "WEB",
      "url": "https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/symfony/CVE-2026-109413.yaml"
    },
    {
      "type": "WEB",
      "url": "https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/yaml/CVE-2026-109413.yaml"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/symfony/symfony"
    },
    {
      "type": "WEB",
      "url": "https://github.com/symfony/symfony/releases/tag/v5.4.54"
    },
    {
      "type": "WEB",
      "url": "https://github.com/symfony/symfony/releases/tag/v6.4.45"
    },
    {
      "type": "WEB",
      "url": "https://github.com/symfony/symfony/releases/tag/v7.4.18"
    },
    {
      "type": "WEB",
      "url": "https://github.com/symfony/symfony/releases/tag/v8.1.6"
    },
    {
      "type": "WEB",
      "url": "https://symfony.com/blog/cve-2026-109413-unbounded-recursion-in-the-yaml-inline-lexer-lets-a-single-document-crash-the-process"
    },
    {
      "type": "WEB",
      "url": "https://symfony.com/cve-2026-109413"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Symfony: Unbounded Recursion in the YAML Inline Lexer Lets a Single Document Crash the Process"
}



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