GHSA-c2p3-7m5p-cv8x Symfony hardened the parser when handling untrusted input

• Packagist symfony/yaml: < 5.4.52 → fixed in 5.4.52 • Packagist symfony/symfony: < 5.4.52 → fixed in 5.4.52 • Packagist symfony/symfony: >= 6.0.0, < 6.4.40 → fixed in 6.4.40 • Packagist symfony/symfony: >= 7.0.0, < 7.4.12 → fixed in 7.4.12 • Packagist symfony/symfony: >= 8.0.0, < 8.0.12 → fixed in 8.0.12 • Packagist symfony/yaml: >= 6.0.0, < 6.4.40 → fixed in 6.4.40 • Packagist symfony/yaml: >= 7.0.0, < 7.4.12 → fixed in 7.4.12 • Packagist symfony/yaml: >= 8.0.0, < 8.0.12 → fixed in 8.0.12

Description `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. Resolution The `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()`. The patch for this issue is available here for branch 5.4. Credits Symfony would like to thank Pietro Tirenna (Shielder) for reporting the issue and Nicolas Grekas for fixing it.