CVE-2026-45304CWE-776

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

High · published July 14, 2026

CVSS v4.0
8.7
EPSS
1%
Percentile
52.0
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v4.0
8.7 · HIGH
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
EPSS
0.00684 · 52.0th percentile
Weakness
CWE-776 · Improper Restriction of Recursive Entity References in DTDs ('XML Entity Expansion')
Published
2026-07-14T18:48Z
EPSS history
Timeline
  • 14 JUL 18:48Z
    Symfony: YAML Parser Exponential Memory Allocation via Recursive Collection-Alias Expansion ("Billion Laughs")
    cvelistv5