What’s Vulnerable › Vulnerabilities

CVE-2026-45305: Symfony: YAML Parser ReDoS via Catastrophic Backtracking in Parser::cleanup() Regex

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.7% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-07-14 · updated 2026-07-15
• Weakness: CWE-1333

Description

Symfony is a PHP framework for web and console applications and a set of reusable PHP components. Prior to 5.4.52, 6.4.40, 7.4.12, and 8.0.12, Symfony\Component\Yaml\Parser::cleanup() used regular expressions with overlapping quantifiers for YAML directive, comment, and document marker cleanup, allowing crafted input to make parsing hang for an arbitrarily long time. This issue is fixed in versions 5.4.52, 6.4.40, 7.4.12, and 8.0.12.

Affected products

• symfony: before 5.4.52; from 6.0.0 before 6.4.40; from 7.0.0 before 7.4.12; from 8.0.0 before 8.0.12 — fixed in 5.4.52, 6.4.40, 7.4.12, 8.0.12

How to fix

Upgrade to a fixed version: symfony 5.4.52, 6.4.40, 7.4.12, 8.0.12. Check the vendor advisory for mitigations.

References

• https://github.com/symfony/symfony/commit/9749cd43c5e09b3735093623670b21b9d8a056cb
• https://github.com/symfony/symfony/releases/tag/v5.4.52
• https://github.com/symfony/symfony/releases/tag/v6.4.40
• https://github.com/symfony/symfony/releases/tag/v7.4.12
• https://github.com/symfony/symfony/releases/tag/v8.0.12
• https://github.com/symfony/symfony/security/advisories/GHSA-9frc-8383-795m

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