CVE-2026-45304

Symfony: YAML Parser Exponential Memory Allocation via Recursive Collection-Alias Expansion ("Billion Laughs")

Published: Jul 14, 2026Updated: Jul 15, 2026 Sources: CVE List NVDCWE-776

7.5HIGH

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 resolved YAML collection aliases recursively, allowing a small untrusted YAML input to expand into a multi-gigabyte structure and exhaust memory. This issue is fixed in versions 5.4.52, 6.4.40, 7.4.12, and 8.0.12.

No summary for this CVE yet.

CVSS Vector Breakdown

Exploitability

AV:NAttack Vector

Network

AC:LAttack Complexity

Low

PR:NPrivileges Required

None

UI:NUser Interaction

None

Scope

S:UScope

Unchanged

Impact

C:NConfidentiality

None

I:NIntegrity

None

A:HAvailability

High

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Weaknesses

CWE-776

Affected Products

symfony

oss-projectaka twig (related), symfony framework

symfonyLibrary

OSS Libraries / web-framework

yamlLibrary

OSS Libraries / web-framework

sensiolabs

oss-project

symfonyLibraryLibrary

OSS Libraries / generic-library

Exploitability

Official Patch Available

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Attack Graph

Products CVE Techniques Tactics

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MITRE ATT&CK

1 technique

Impact

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References

https://github.com/symfony/symfony/security/advisories/GHSA-4qpc-3hr4-r2p4

github.com

https://github.com/symfony/symfony/commit/e77391b2e4f18821198f010d573674c8ed4a970a

github.com

https://github.com/symfony/symfony/releases/tag/v5.4.52

github.com

and 3 more references View all →

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