CVE-2026-45304

HIGH 8.7 ALL-YEARS

Published 2026-07-14 · Last modified 2026-07-14 · GitHub_M · NVD: Analyzed

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.

ELEVATED IMPACT

Severe if exploited (CVSS 8.7), but no confirmed exploitation. Patch on a normal cadence.

Exploitation likelihood

0.8%chance of exploitation in 30 days · 54th percentile

○ In CISA KEV○ Public exploit / PoC◆ SSVC: exploitation none, automatable yes

Impact if exploited

8.7CVSS 4.0 · HIGH · CNA

ConfidentialityNone
IntegrityNone
AvailabilityHigh

What an attacker needs

✓Access: Reachable over the network — no local access needed
✓Privileges: No account or privileges required
✓User interaction: No user interaction needed
✓Complexity: No special conditions — reliably repeatable
✓Requirements: No special attack requirements

✓ lowers the bar for an attacker · ⚠ raises it

Proof of concept & exploit code

No public exploit or proof-of-concept code is catalogued for this CVE (no ExploitDB, Nuclei, or CISA-KEV entry). It may still exist — search GitHub or check the references below.

Affected

Vendors Symfony Sensiolabs

Products Symfony Yaml

Weakness (CWE)

CWE-776: : Improper Restriction of Recursive Entity References in DTDs ('XML Entity Expansion')

CVSS vector

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

Known Affected Software Configurations

Vendor	Product	Version range
Sensiolabs	Symfony	< 5.4.52
Sensiolabs	Symfony	≥ 6.0.0 and < 6.4.40
Sensiolabs	Symfony	≥ 7.0.0 and < 7.4.12
Sensiolabs	Symfony	≥ 8.0.0 and < 8.0.12

All CVSS metrics

HIGH 8.7 v4.0 · CNA Primary
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
HIGH 8.7 v4.0 · NVD Secondary
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
HIGH 7.5 v3.1 · NVD Primary
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References

Patches & mitigations

https://github.com/symfony/symfony/security/advisories/GHSA-4qpc-3hr4-r2p4 x_refsource_CONFIRMPatchVendor Advisory
https://github.com/symfony/symfony/commit/e77391b2e4f18821198f010d573674c8ed4a970a x_refsource_MISCPatch

Technical & other

https://github.com/symfony/symfony/releases/tag/v5.4.52 x_refsource_MISCProductRelease Notes
https://github.com/symfony/symfony/releases/tag/v6.4.40 x_refsource_MISCProductRelease Notes
https://github.com/symfony/symfony/releases/tag/v7.4.12 x_refsource_MISCProductRelease Notes
https://github.com/symfony/symfony/releases/tag/v8.0.12 x_refsource_MISCProductRelease Notes

Sources: NVD · CVE.org · EPSS