High 8.7Published Jul 14, 2026

CVE-2026-45304Symfony: YAML Parser Exponential Memory Allocation via Recursive Collection-Alias Expansion ("Billion Laughs")

Updated under an hour ago (Oct 27, 2026, 8:23 AM ET)

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It affects symfony and 2 other products. Add what you run to find out whether that includes you.

No exploitation reported and no EPSS estimate yet.

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Every CVE for symfony

Exploited in the last 30 days

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.

CVSS: 8.7 HIGH (v4.0, CNA)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
Weakness (CWE): CWE-776
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: GitHub_M
NVD analysis: Analyzed
Record last updated: Jul 14, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

symfony symfony symfony:symfony (from the name)	before 5.4.52; from 6.0.0-BETA1, < 6.4.40; from 7.0.0-BETA1, < 7.4.12; from 8.0.0-BETA1, < 8.0.12	CNA record
symfony yaml symfony:yaml (from the name)	before 5.4.52; from 6.0.0-BETA1, < 6.4.40; from 7.0.0-BETA1, < 7.4.12; from 8.0.0-BETA1, < 8.0.12	CNA record
sensiolabs symfony sensiolabs:symfony	before 5.4.52; from 6.0.0 before 6.4.40; from 7.0.0 before 7.4.12; from 8.0.0 before 8.0.12	NVD

References

References

https://github.com/symfony/symfony/security/advisories/GHSA-4qpc-3hr4-r2p4	x-refsource-confirm, patch, vendor-advisory
https://github.com/symfony/symfony/commit/e77391b2e4f18821198f010d573674c8ed4a970a	x-refsource-misc, patch
https://github.com/symfony/symfony/releases/tag/v5.4.52	x-refsource-misc, product, release-notes
https://github.com/symfony/symfony/releases/tag/v6.4.40	x-refsource-misc, product, release-notes
https://github.com/symfony/symfony/releases/tag/v7.4.12	x-refsource-misc, product, release-notes
https://github.com/symfony/symfony/releases/tag/v8.0.12	x-refsource-misc, product, release-notes

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.