Symfony: Unbounded Recursion in the YAML Inline Lexer Lets a Single Document Crash the Process
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.
CVE-2026-109413
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: cve:CVE-2026-109413
symfony
Source reference: /containers/cna/affected/0/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"repo": "https://github.com/symfony/yaml",
"vendor": "sensiolabs",
"modules": [
"Symfony\\\\Component\\\\Yaml\\\\Parser::lexInlineStructure()"
],
"product": "symfony",
"versions": [
{
"status": "affected",
"version": "0",
"lessThan": "v5.4.54",
"versionType": "git"
},
{
"status": "affected",
"version": "v6.0.0-BETA1",
"lessThan": "v6.4.45",
"versionType": "git"
},
{
"status": "affected",
"version": "v7.0.0-BETA1",
"lessThan": "v7.4.18",
"versionType": "git"
},
{
"status": "affected",
"version": "v8.0.0-BETA1",
"lessThan": "v8.1.6",
"versionType": "git"
}
],
"packageName": "symfony/yaml",
"collectionURL": "https://packagist.org/packages/symfony/yaml",
"defaultStatus": "unaffected"
}
]- Related CVEs
- CVE-2026-109413
Source reference:
/cveMetadata/cveId
Publisher severity
high
Source reference: /containers/cna/metrics
- Event
- #29969 · Revision 1
- Added to Heist Feed
- Publisher date