SB2026101517 - Uncontrolled Recursion in Symfony

Description

This security bulletin contains information about 1 vulnerability.

1) Uncontrolled Recursion (CVE-ID: CVE-2026-109413)

CWE-ID: CWE-674 - Uncontrolled Recursion

CVSSv4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]

The vulnerability allows a remote attacker to cause a denial of service.

The vulnerability exists due to uncontrolled recursion in Symfony's YAML inline lexer, specifically YamlParser::lexInlineStructure(), when lexing deeply nested inline collections without enforcing the parser's nesting limit. A remote attacker can submit a single specially crafted YAML request to exhaust the stack and cause a denial of service through a process crash or fatal request error.

Exploitation through #[MapRequestPayload] requires the Yaml component to be installed and the endpoint to accept YAML without an acceptFormat restriction. Whether stack exhaustion crashes the process or terminates the request with a fatal error depends on the PHP version and stack settings.

Remediation

Install update from vendor's website.

References

• https://github.com/symfony/symfony/security/advisories/GHSA-2v3c-qxhr-7vpv
• https://github.com/symfony/symfony/commit/2a8bf9c58d862b0c76a35ce288d1ba6a27223aad