XXE in Sensiolabs Symfony
CVE-2026-45304
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
EPSS exploit prediction
EPSS: 0.007 (51.2th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 51st percentile — 51.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.007 · newest: 0.007 · change: 0.000
Affected products
- Sensiolabs Symfony
- Symfony — versions < 5.4.52, >= 6.0.0-BETA1, < 6.4.40, >= 7.0.0-BETA1, < 7.4.12
- Symfony Yaml — versions < 5.4.52, >= 6.0.0-BETA1, < 6.4.40, >= 7.0.0-BETA1, < 7.4.12
Weakness classification (CWE)
References
- github.com/symfony/symfony/security/advisories/GHSA-4qpc-3hr4-r2p4 (Patch, Vendor Advisory)
- github.com/symfony/symfony/commit/e77391b2e4f18821198f010d573674c8ed4a970a (Patch)
- github.com/symfony/symfony/releases/tag/v5.4.52 (Product, Release Notes)
- github.com/symfony/symfony/releases/tag/v6.4.40 (Product, Release Notes)
- github.com/symfony/symfony/releases/tag/v7.4.12 (Product, Release Notes)
- github.com/symfony/symfony/releases/tag/v8.0.12 (Product, Release Notes)
Frequently asked questions
- What is CVE-2026-45304?
- CVE-2026-45304 is a high-severity vulnerability in Sensiolabs Symfony, classified under Improper Restriction of Recursive Entity References in DTDs (XML Entity Expansion). CVSS score: 7.5/10. Published 2026-07-14.
- How severe is CVE-2026-45304?
- High severity. CVSS v3 base score is 7.5 out of 10.