Vulnerability · Published Jul 14, 2026 · Assigned by GitHub_M
CVE-2026-45304Symfony: YAML Parser Exponential Memory Allocation via Recursive Collection-Alias Expansion ("Billion Laughs")
High 8.7
In plain English
A high-severity security flaw in symfony from symfony. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.7% (higher than 53% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | symfony | 5.4.53+dfsg-0+deb12u1 | DEBIAN-CVE-2026-45304 |
| Debian:13 | symfony | 6.4.41+dfsg-0+deb13u1 | DEBIAN-CVE-2026-45304 |
| Debian:14 | symfony | 7.4.12+dfsg-1 | DEBIAN-CVE-2026-45304 |
| Packagist | symfony/symfony | 7.4.12 | GHSA-4qpc-3hr4-r2p4 |
| Packagist | symfony/symfony | 8.0.12 | GHSA-4qpc-3hr4-r2p4 |
| Packagist | symfony/symfony | 5.4.52 | GHSA-4qpc-3hr4-r2p4 |
| Packagist | symfony/symfony | 6.4.40 | GHSA-4qpc-3hr4-r2p4 |
| Packagist | symfony/yaml | 5.4.52 | GHSA-4qpc-3hr4-r2p4 |
| Packagist | symfony/yaml | 6.4.40 | GHSA-4qpc-3hr4-r2p4 |
| Packagist | symfony/yaml | 7.4.12 | GHSA-4qpc-3hr4-r2p4 |
| Packagist | symfony/yaml | 8.0.12 | GHSA-4qpc-3hr4-r2p4 |
| Ubuntu:25.10 | symfony | no fix listed | UBUNTU-CVE-2026-45304 |
| Ubuntu:26.04:LTS | symfony | no fix listed | UBUNTU-CVE-2026-45304 |
| Ubuntu:26.10 | symfony | no fix listed | UBUNTU-CVE-2026-45304 |
Affected products (as reported)
Weakness: CWE-776 · 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
References
- 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