{
"id": "GHSA-9frc-8383-795m",
"aliases": [
"CVE-2026-45305"
],
"details": "### Description\n\n`Symfony\\Component\\Yaml\\Parser::cleanup()` strips the optional `%YAML` directive header, leading comments, and document start/end markers before parsing. The original regexes contained overlapping quantifiers, most notably `'#^%YAML[: ][\\d.]+.*\\n#u'`, whose `[\\d.]+` and `.*` overlap on the dot, that exhibit catastrophic backtracking on crafted input. A single oversized `%YAML` directive header (or comment / document-marker line) makes the parser hang for an arbitrarily long time, denying service.\n\n### Resolution\n\nThe four regexes in `Parser::cleanup()` (YAML directive header, leading comments, document-start marker, document-end marker) have been rewritten with possessive quantifiers and unambiguous character classes so backtracking cannot occur.\n\nThe patch for this issue is available [here](https://github.com/symfony/symfony/commit/9749cd43c5e09b3735093623670b21b9d8a056cb) for branch 5.4.\n\n### Credits\n\nSymfony would like to thank Pietro Tirenna (Shielder) for reporting the issue and Nicolas Grekas for fixing it.",
"summary": "Symfony's YAML Parser has a ReDoS via Catastrophic Backtracking in Parser::cleanup() Regex",
"affected": [
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
},
{
"fixed": "5.4.52"
}
]
}
],
"package": {
"name": "symfony/yaml",
"ecosystem": "Packagist"
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
},
{
"fixed": "5.4.52"
}
]
}
],
"package": {
"name": "symfony/symfony",
"ecosystem": "Packagist"
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "6.0.0"
},
{
"fixed": "6.4.40"
}
]
}
],
"package": {
"name": "symfony/symfony",
"ecosystem": "Packagist"
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "7.0.0"
},
{
"fixed": "7.4.12"
}
]
}
],
"package": {
"name": "symfony/symfony",
"ecosystem": "Packagist"
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "8.0.0"
},
{
"fixed": "8.0.12"
}
]
}
],
"package": {
"name": "symfony/symfony",
"ecosystem": "Packagist"
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "6.0.0"
},
{
"fixed": "6.4.40"
}
]
}
],
"package": {
"name": "symfony/yaml",
"ecosystem": "Packagist"
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "7.0.0"
},
{
"fixed": "7.4.12"
}
]
}
],
"package": {
"name": "symfony/yaml",
"ecosystem": "Packagist"
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "8.0.0"
},
{
"fixed": "8.0.12"
}
]
}
],
"package": {
"name": "symfony/yaml",
"ecosystem": "Packagist"
}
}
],
"modified": "2026-05-27T21:34:36Z",
"severity": [
{
"type": "CVSS_V4",
"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:U"
}
],
"published": "2026-05-27T21:34:35Z",
"references": [
{
"url": "https://github.com/symfony/symfony/security/advisories/GHSA-9frc-8383-795m",
"type": "WEB"
},
{
"url": "https://github.com/symfony/symfony/commit/9749cd43c5e09b3735093623670b21b9d8a056cb",
"type": "WEB"
},
{
"url": "https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/symfony/CVE-2026-45305.yaml",
"type": "WEB"
},
{
"url": "https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/yaml/CVE-2026-45305.yaml",
"type": "WEB"
},
{
"url": "https://github.com/symfony/symfony",
"type": "PACKAGE"
},
{
"url": "https://symfony.com/cve-2026-45305",
"type": "WEB"
}
],
"schema_version": "1.4.0",
"database_specific": {
"cwe_ids": [
"CWE-1333"
],
"severity": "LOW",
"github_reviewed": true,
"nvd_published_at": null,
"github_reviewed_at": "2026-05-27T21:34:35Z"
}
}