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Fencer Intel
high 8.7

CVE-2026-109413 json

Symfony: Unbounded Recursion in the YAML Inline Lexer Lets a Single Document Crash the Process

published 25d ago modified 13d ago also GHSA-2v3c-qxhr-7vpv , EUVD-2026-102109

cvss
8.7
version 4.0, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 34%
public exploits
0
none known

Summary

In Symfony YAML prior to versions 5.4.54, 6.4.45, 7.4.18, and 8.1.6, Yaml\Parser::lexInlineStructure() recursed through lexInlineMapping() and lexInlineSequence() for every { and [ of an inline collection, without entering the nesting level that the rest of the parser bounds with maxNestingLevel. A document made of deeply nested inline collections, such as [[[[...]]]], exhausted the stack while it was being lexed: depending on the PHP version and its stack settings, the process crashed or the request ended with a fatal error.

Any code parsing untrusted YAML is affected. That includes #[MapRequestPayload] when the Yaml component is installed and the endpoint does not restrict acceptFormat: a single unauthenticated request with a YAML content type is enough.

This issue affects symfony/yaml through v5.4.53, v6.0.0-BETA1 through v6.4.44, v7.0.0-BETA1 through v7.4.17, and v8.0.0-BETA1 through v8.1.5.

Patch / fix

  • packagist symfony/symfony 5.4.54, 6.4.45, 7.4.18, 8.1.6
  • packagist symfony/yaml 5.4.54, 6.4.45, 7.4.18, 8.1.6
  • symfony Debian 13 6.4.49+dfsg-0+deb13u1
  • symfony Debian 14 7.4.18+dfsg-1

debian advisories DEBIAN-CVE-2026-109413

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Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-109413 updated cvss 7.5

symfony/yaml: symfony/yaml: Denial of Service via deeply nested inline collections

  • Red Hat All currently supported Red Hat products
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
partial
Assessed
25d ago

Exploit prediction

0.40% chance of exploitation in the next 30 days, higher than 34% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
CNA 4.0 8.7 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
CNA 4.0 8.7 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/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

Affected packages

ecosystem package affected fixed in
packagist symfony/symfony
>=2.0.0, <5.4.54
>=6.0.0, <6.4.45
>=7.0.0, <7.4.18
>=8.0.0, <8.1.6
5.4.54
6.4.45
7.4.18
8.1.6
packagist symfony/yaml
>=2.0.0, <5.4.54
>=6.0.0, <6.4.45
>=7.0.0, <7.4.18
>=8.0.0, <8.1.6
5.4.54
6.4.45
7.4.18
8.1.6

Affected products

  • sensiolabs symfony

Classification

Weakness

References

Sources

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