High 8.7Published Oct 15, 2026

CVE-2026-109413Symfony: Unbounded Recursion in the YAML Inline Lexer Lets a Single Document Crash the Process

Updated under an hour ago (2026-10-19 06:30 UTC)

Does this affect you?

It affects sensiolabs symfony. Add what you run to find out whether that includes you.

EPSS puts the chance of exploitation in the next 30 days at 0.51%, higher than 42% of scored CVEs.

Do this next

Start free and add your stack

Free account, 1 product

Every CVE for sensiolabs symfony

Exploited in the last 30 days

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.

CVSS: 8.7 HIGH (v4.0, CNA)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
Weakness (CWE): CWE-674
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): 0.51% (percentile 42)
Assigned by: Checkmarx
NVD analysis: Awaiting Analysis
Record last updated: Oct 15, 2026
First seen by InfoSec Signals: Oct 15, 2026

Affected products

Affected products

sensiolabs symfony sensiolabs:symfony (from the name)	before v5.4.54; from v6.0.0-BETA1 before v6.4.45; from v7.0.0-BETA1 before v7.4.18; from v8.0.0-BETA1 before v8.1.6	CNA record

References

https://github.com/symfony/symfony/security/advisories/GHSA-2v3c-qxhr-7vpvthird-party-advisory
https://symfony.com/blog/cve-2026-109413-unbounded-recursion-in-the-yaml-inline-lexer-lets-a-single-document-crash-the-processvendor-advisory
https://github.com/symfony/symfony/pull/65688patch

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.