Symfony's YAML Parser has a ReDoS via Catastrophic Backtracking in Parser::cleanup() Regex
Description
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.
Resolution
The 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.
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.
Software afectado
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| Plataforma | Paquete | Versiones vulnerables | Corregida en |
|---|---|---|---|
| Paquete de Composer | symfony/symfony | < 5.4.52, >= 6.0.0, < 6.4.40, >= 7.0.0, < 7.4.12, >= 8.0.0, < 8.0.12 | 5.4.52, 6.4.40, 7.4.12, 8.0.12 |
| Paquete de Composer | symfony/yaml | < 5.4.52, >= 6.0.0, < 6.4.40, >= 7.0.0, < 7.4.12, >= 8.0.0, < 8.0.12 | 5.4.52, 6.4.40, 7.4.12, 8.0.12 |
Referencias
- https://github.com/symfony/symfony/security/advisories/GHSA-9frc-8383-795m
- https://github.com/symfony/symfony/commit/9749cd43c5e09b3735093623670b21b9d8a056cb
- https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/symfony/CVE-2026-45305.yaml
- https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/yaml/CVE-2026-45305.yaml
- https://github.com/symfony/symfony
- https://symfony.com/cve-2026-45305
- Vector CVSS
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- Debilidad (CWE)
CWE-1333- Plataforma
- Composer
- Paquete
symfony/symfony, symfony/yaml- Publicada
- 27.05.2026
- Actualizado
- 11.10.2026 10:22
Fuentes y licencias
OSV / GitHub Advisory Database - GHSA-9frc-8383-795m - CC BY 4.0
Historial de vulnerabilidades: symfony/yaml
Todas las vulnerabilidades publicadas de este paquete (Paquete de Composer), de la más reciente a la más antigua. Muestra si es un fallo aislado o un paquete que hay que vigilar.
- Entradas en total
- 5
- Primera → última
- 05.2022 05.2026
- Sin corrección
- 0
- Explotada en ataques
- 0
Distribución por gravedad
- Alta 2
- Baja 3
Divulgaciones por año
- 2022: 2
- 2023: 0
- 2024: 0
- 2025: 0
- 2026: 3
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Symfony's YAML Parser has a ReDoS via Catastrophic Backtracking in Parser::cleanup() Regex esta entrada
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