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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
NVD MITRE
EPSS Score
0.8%
Top 46.7%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
Patch Available
Self-Check
OpenVAS

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

AV:NAC:LPR:NUI:NS:UC:NI:NA:H
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 symfony framework, twig (related)
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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