PT-2026-44146 · Symfony · Symfony

Published 2026-05-21 · Updated 2026-05-27 · CVE-2026-45133

Positive Technologies (AI Summary)

CVSS v4.0

2.7

Low

Base vector

AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:U

Name of the Vulnerable Software and Affected Versions Symfony versions prior to 5.4.21

Description The SymfonyComponentYamlParser entry point for parsing YAML strings into PHP values via Yaml::parse() lacks a depth limit for recursion. When processing attacker-controlled input, deeply nested mappings or sequences cause the block-level Parser::parseBlock() and inline Inline::parseSequence() or Inline::parseMapping() parsers to recurse indefinitely. This leads to PHP stack exhaustion and crashes the worker process.

Recommendations Update to version 5.4.21 or later. As a temporary mitigation, restrict the use of Yaml::parse() and Yaml::parseFile() with untrusted user input.

Exploit

Fix

Uncontrolled Recursion

DoS

XML Entity Expansion

Weakness Enumeration

CWE-674

CWE-1333

CWE-776

Related Identifiers

CVE-2026-45133

GHSA-C2P3-7M5P-CV8X

Affected Products

Symfony

References · 13

• 🔥 https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/symfony/CVE-2026-45133.yaml · Exploit
• 🔥 https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/yaml/CVE-2026-45133.yaml · Exploit
• https://osv.dev/vulnerability/DEBIAN-CVE-2026-45133 · Vendor Advisory
• https://osv.dev/vulnerability/GHSA-c2p3-7m5p-cv8x · Vendor Advisory
• https://ubuntu.com/security/CVE-2026-45133 · Vendor Advisory
• https://security-tracker.debian.org/tracker/CVE-2026-45133 · Vendor Advisory
• https://cve.org/CVERecord?id=CVE-2026-45133 · Security Note
• https://osv.dev/vulnerability/UBUNTU-CVE-2026-45133 · Vendor Advisory
• https://github.com/symfony/symfony · Note
• https://github.com/symfony/symfony/security/advisories/GHSA-c2p3-7m5p-cv8x · Note
• https://github.com/symfony/symfony/commit/914f427ed9630ddb3904dafba763e53d9f133fe3 · Note
• https://symfony.com/blog/cve-2026-45133-yaml-parser-stack-exhaustion-via-unbounded-recursion-in-nested-blocks-sequences-and-mappings · Note
• https://symfony.com/cve-2026-45133 · Note