{"id":"CVE-2026-45133","aliases":["GHSA-c2p3-7m5p-cv8x"],"url":"https://o3.security/vulnerability/CVE-2026-45133","summary":"Symfony: [Yaml] Harden the parser when handling untrusted input","details":"### Description\n\n`Symfony\\Component\\Yaml\\Parser` is the entry point for parsing YAML strings into PHP values via `Yaml::parse()`. When the parser is exposed to attacker-controlled input, deeply nested mappings or sequences cause both the block-level (`Parser::parseBlock()`) and inline (`Inline::parseSequence()` / `Inline::parseMapping()`) parsers to recurse without a depth limit. A crafted document exhausts the PHP stack and crashes the worker.\n\n### Resolution\n\nThe `Parser` now tracks recursion depth in a shared `ParserState` object across both block-level and inline parsing, with a default limit of **128**. The limit is configurable via a new `$maxNestingLevel` argument on `Parser::__construct()`, `Yaml::parse()` and `Yaml::parseFile()`.\n\nThe patch for this issue is available [here](https://github.com/symfony/symfony/commit/914f427ed9630ddb3904dafba763e53d9f133fe3) 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.","published":"2026-07-14T18:45:03.458Z","modified":"2026-08-12T03:51:22.618642201Z","cvss":null,"epss":{"score":0.0063,"percentile":0.48594,"asOf":"2026-09-17"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Packagist","name":"symfony/yaml","fixedVersion":"5.4.52"},{"ecosystem":"Packagist","name":"symfony/symfony","fixedVersion":"5.4.52"},{"ecosystem":"Packagist","name":"symfony/symfony","fixedVersion":"6.4.40"},{"ecosystem":"Packagist","name":"symfony/symfony","fixedVersion":"7.4.12"},{"ecosystem":"Packagist","name":"symfony/symfony","fixedVersion":"8.0.12"},{"ecosystem":"Packagist","name":"symfony/yaml","fixedVersion":"6.4.40"},{"ecosystem":"Packagist","name":"symfony/yaml","fixedVersion":"7.4.12"},{"ecosystem":"Packagist","name":"symfony/yaml","fixedVersion":"8.0.12"}],"fix":{"url":"https://github.com/symfony/symfony/commit/914f427ed9630ddb3904dafba763e53d9f133fe3","label":"symfony/symfony@914f427"},"references":[{"type":"WEB","url":"https://github.com/symfony/symfony/releases/tag/v5.4.52"},{"type":"WEB","url":"https://github.com/symfony/symfony/releases/tag/v6.4.40"},{"type":"WEB","url":"https://github.com/symfony/symfony/releases/tag/v7.4.12"},{"type":"WEB","url":"https://github.com/symfony/symfony/releases/tag/v8.0.12"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/45xxx/CVE-2026-45133.json"},{"type":"ADVISORY","url":"https://github.com/symfony/symfony/security/advisories/GHSA-c2p3-7m5p-cv8x"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-45133"},{"type":"WEB","url":"https://github.com/symfony/symfony/commit/914f427ed9630ddb3904dafba763e53d9f133fe3"},{"type":"WEB","url":"https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/symfony/CVE-2026-45133.yaml"},{"type":"WEB","url":"https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/yaml/CVE-2026-45133.yaml"},{"type":"PACKAGE","url":"https://github.com/symfony/symfony"},{"type":"WEB","url":"https://symfony.com/cve-2026-45133"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:22.618642201Z"}}