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Fencer Vulns
high 7.5

CVE-2026-45133 json

Symfony: [Yaml] Harden the parser when handling untrusted input

published 2026-05-27 5 mo ago modified 2026-09-10 1 mo ago also GHSA-c2p3-7m5p-cv8x , EUVD-2026-44351

cvss
7.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.6%
EPSS 0.6% chance of exploitation in 30 days, percentile 50%
public exploits
0
none known

Summary

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, when the parser is exposed to attacker-controlled input, deeply nested mappings or sequences cause both the block-level (Parser::parseBlock()) and inline (Inline::parseSequence() / Inline::parseMapping()) parsers to recurse without a depth limit. A crafted document exhausts the PHP stack and crashes the worker. This issue is fixed in versions 5.4.52, 6.4.40, 7.4.12, and 8.0.12.

Patch / fix

  • packagist symfony/yaml 5.4.52, 6.4.40, 7.4.12, 8.0.12
  • packagist symfony/symfony 5.4.52, 6.4.40, 7.4.12, 8.0.12
  • sensiolabs symfony 5.4.52, 6.4.40, 7.4.12, 8.0.12
  • symfony Debian 12 5.4.53+dfsg-0+deb12u1
  • symfony Debian 13 6.4.41+dfsg-0+deb13u1
  • symfony Debian 14 7.4.12+dfsg-1

debian advisories DEBIAN-CVE-2026-45133

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
3 mo ago

Exploit prediction

0.63% chance of exploitation in the next 30 days, higher than 50% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 4.0 8.2 CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
CNA 4.0 8.2 CVSS:4.0/AV:N/AC:L/AT:P/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
NVD 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected packages

ecosystem package affected fixed in
packagist symfony/yaml
<5.4.52
>=6.0.0, <6.4.40
>=7.0.0, <7.4.12
>=8.0.0, <8.0.12
5.4.52
6.4.40
7.4.12
8.0.12
packagist symfony/symfony
<5.4.52
>=6.0.0, <6.4.40
>=7.0.0, <7.4.12
>=8.0.0, <8.0.12
5.4.52
6.4.40
7.4.12
8.0.12

Affected products

  • symfony symfony

Classification

Weakness
  • CWE-674 Uncontrolled Recursion
  • CWE-776 Improper Restriction of Recursive Entity References in DTDs
  • CWE-1333 Inefficient Regular Expression Complexity

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.