Uncontrolled Recursion in Symfony - CVE-2026-109449

Vulnerability details

The vulnerability allows a remote attacker to cause a denial of service by crashing the PHP process.

The vulnerability exists due to uncontrolled node-tree depth in the ExpressionLanguage parser when parsing untrusted expressions. A remote attacker can submit expressions containing deeply nested unary operators, array literals, binary operators or property accesses to cause a denial of service by crashing the PHP process.

The ExpressionSyntax validation constraint passes user-supplied expressions to ExpressionLanguage::lint(), exposing applications that validate such expressions to exploitation through a single request.

Affected software

How to mitigate CVE-2026-109449

External References

• https://github.com/symfony/symfony/security/advisories/GHSA-7rpj-w9pf-39rr
• https://github.com/symfony/symfony/commit/c2c00c5c15602aa2df98c3e2b313570ab5f26a33

Related Security Bulletins

• Uncontrolled Recursion in Symfony