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

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-109413
StatePUBLISHED
AssignerCheckmarx
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-15 15:17:24 UTC
Updated2026-10-16 16:00:33 UTC
DescriptionIn 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.

Risk And Classification

Primary CVSS: v4.0 8.7 HIGH from 596c5446-0ce5-4ba2-aa66-48b3b757a647

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

Problem Types: CWE-674 | CWE-674 CWE-674 Uncontrolled Recursion

VersionSourceTypeScoreSeverityVector
4.0596c5446-0ce5-4ba2-aa66-48b3b757a647Secondary8.7HIGHCVSS: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/C...
4.0CNACVSS8.7HIGHCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

CVSS v4.0 Breakdown

Attack Vector
Network
Attack Complexity
Low
Attack Requirements
None
Privileges Required
None
User Interaction
None
Confidentiality
None
Integrity
None
Availability
High
Sub Conf.
None
Sub Integrity
None
Sub Availability
None

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Sensiolabs Symfony affected v5.4.54 git Not specified
CNA Sensiolabs Symfony affected v6.0.0-BETA1 v6.4.45 git Not specified
CNA Sensiolabs Symfony affected v7.0.0-BETA1 v7.4.18 git Not specified
CNA Sensiolabs Symfony affected v8.0.0-BETA1 v8.1.6 git Not specified

References

ReferenceSourceLinkTags
symfony.com/blog/cve-2026-109413-unbounded-recursion-in-the-yaml-inline-l... 596c5446-0ce5-4ba2-aa66-48b3b757a647 symfony.com
github.com/symfony/symfony/security/advisories/GHSA-2v3c-qxhr-7vpv 596c5446-0ce5-4ba2-aa66-48b3b757a647 github.com
github.com/symfony/symfony/pull/65688 596c5446-0ce5-4ba2-aa66-48b3b757a647 github.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: Nicolas Grekas (en)

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