CVE Catalog

CVE-2026-109413

HighCVSS 8.7
Published: Updated: Translated: NVD NIST

Exploitation Probability (EPSS)

Low risk
0.51%

42th percentile - higher than 42% of all known CVEs

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 being lexed, causing the process to crash or the request to end with a fatal error. Any code parsing untrusted YAML is affected, including #[MapRequestPayload] when the Yaml component is installed and the endpoint does not restrict acceptFormat.

Risk Assessment

A single unauthenticated request with a YAML content type can crash the process or cause a fatal error, leading to denial of service. This affects any application parsing untrusted YAML, including endpoints using #[MapRequestPayload] without restricting acceptFormat.

Recommendation

Update symfony/yaml to version 5.4.54, 6.4.45, 7.4.18, or 8.1.6 (or later). Additionally, restrict accepted formats on endpoints that accept input to exclude untrusted YAML.

Related vulnerabilities

Original NVD description (English source)

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.

Vulnerability data from NVD (NIST) · CISA KEV · EPSS