Vulnerability details
CVE-2026-45304
symfony symfonysymfony yaml
Symfony: YAML Parser Exponential Memory Allocation via Recursive Collection-Alias Expansion ("Billion Laughs")
CVSS 4.0
8.7High
Official 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.
CVSS scores
| Score | Version | Source | Vector |
|---|---|---|---|
| 8.7High | 4.0 | CVEProject cvelistV5 (CNA) (GitHub_M) | 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 |
Affected products
| Vendor | Product | Versions | Source |
|---|---|---|---|
| symfony | symfony | < 5.4.52 | CVEProject cvelistV5 (CNA) |
| symfony | symfony | >= 6.0.0-BETA1, < 6.4.40 | CVEProject cvelistV5 (CNA) |
| symfony | symfony | >= 7.0.0-BETA1, < 7.4.12 | CVEProject cvelistV5 (CNA) |
| symfony | symfony | >= 8.0.0-BETA1, < 8.0.12 | CVEProject cvelistV5 (CNA) |
| symfony | yaml | < 5.4.52 | CVEProject cvelistV5 (CNA) |
| symfony | yaml | >= 6.0.0-BETA1, < 6.4.40 | CVEProject cvelistV5 (CNA) |
| symfony | yaml | >= 7.0.0-BETA1, < 7.4.12 | CVEProject cvelistV5 (CNA) |
| symfony | yaml | >= 8.0.0-BETA1, < 8.0.12 | CVEProject cvelistV5 (CNA) |
References and advisories
6- https://github.com/symfony/symfony/security/advisories/GHSA-4qpc-3hr4-r2p4 x_refsource_CONFIRM
- https://github.com/symfony/symfony/commit/e77391b2e4f18821198f010d573674c8ed4a970a x_refsource_MISC
- https://github.com/symfony/symfony/releases/tag/v5.4.52 x_refsource_MISC
- https://github.com/symfony/symfony/releases/tag/v6.4.40 x_refsource_MISC
- https://github.com/symfony/symfony/releases/tag/v7.4.12 x_refsource_MISC
- https://github.com/symfony/symfony/releases/tag/v8.0.12 x_refsource_MISC
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Details
- Published
- 2026-07-14
- Last updated
- 2026-07-14
- State
- Published
- Assigner (CNA)
- GitHub_M
Exploit prediction (EPSS)
0.68%
Probability of exploitation in 30 days
52.7%
Percentile (among all CVEs)
SSVC assessment (CISA)
- Automatable
- Yes
- Exploitation
- None
- Technical impact
- Partial
Weaknesses (CWE)
- CWE-776Improper Restriction of Recursive Entity References in DTDs ('XML Entity Expansion')