Uncontrolled Recursion Affecting symfony/yaml package, versions <5.4.52>=6.0.0-BETA1, <6.4.40>=7.0.0-BETA1, <7.4.12>=8.0.0-BETA1, <8.0.12
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-PHP-SYMFONYYAML-16797942
- published22 May 2026
- disclosed20 May 2026
- creditPietro Tirenna
Introduced: 20 May 2026
CVE-2026-45133 (opens in a new tab)How to fix?
Upgrade symfony/yaml to version 5.4.52, 6.4.40, 7.4.12, 8.0.12 or higher.
Overview
Affected versions of this package are vulnerable to Uncontrolled Recursion via Unbounded Recursion in Nested Blocks, Sequences, and Mappings. 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.