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  4. CVE 2026 109449 symfony unbounded nesting in the expression
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Back to active CVEs
High · CVSS 8.7CVE-2026-109449

Symfony: Unbounded Nesting in the Expression Parser Lets Untrusted Expressions Crash the ProcessCVE-2026-109449

Answer in brief

CVE-2026-109449 records a High severity (CVSS 8.7) vulnerability in Symfony: Unbounded Nesting in the Expression Parser Lets Untrusted Expressions Crash the Process. The current sources do not mark it as known exploited. The current feed maps sensiolabs/symfony/expression-language (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Oct 15, 2026Updated Oct 15, 2026Source checked Oct 15, 2026First seen by HOL Oct 15, 2026Material review Oct 15, 2026
Upstream Advisory

Key facts

Risk
High · CVSS 8.7
Exploitation
Not marked as known exploited
Affected software
1 mapped package or product
Fix availability
Available

Why this deserves its current priority

CVSS is 8.7. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps sensiolabs/symfony/expression-language (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
PackageAffected rangeFixed version
sensiolabs/symfony/expression-languagegeneric>=0 <v5.4.54 || >=v6.0.0-BETA1 <v6.4.48 || >=v7.0.0-BETA1 <v7.4.21 || >=v8.0.0-BETA1 <v8.1.9v5.4.54, v6.4.48, v7.4.21, v8.1.9

Recommended response

  1. 1Check inventory. Check lockfiles and deployed manifests for sensiolabs/symfony/expression-language.
  2. 2Review the reported fix. Update sensiolabs/symfony/expression-language to v5.4.54 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

  1. Published upstream

    Oct 15, 2026

    Evidence: source:cvelist:source_dates:source-dates:record

  2. Source modified

    Oct 15, 2026

    Evidence: source:cvelist:source_dates:source-dates:record

  3. First seen by HOL

    Oct 15, 2026

Sources and claim methodology

  • GitHub security advisorygithub.com
  • GitHub security advisorygithub.com
  • GitHub security advisorygithub.com
  • GitHub security advisorygithub.com
  • Source referencesymfony.com
Upstream source description

In Symfony Expression Language versions prior to 5.4.54, 6.4.48, 7.4.21, and 8.1.9, the parser of the ExpressionLanguage component built its node tree with no bound on its depth. An expression made of tens of thousands of nested unary operators, array literals, binary operators or property accesses crashed the PHP process, while the tree was being freed. #[Assert\ExpressionSyntax] passes the validated value to ExpressionLanguage::lint(), so an application validating expressions written by its users could be crashed by a single request, and so could any code parsing untrusted expressions. This issue affects symfony/expression-language through v5.4.53, v6.0.0-BETA1 through v6.4.47, v7.0.0-BETA1 through v7.4.20, and v8.0.0-BETA1 through v8.1.8.

Quoted source text, attributed separately from HOL analysis.

Related CVEs

  • kin-openapi: Uncontrolled Recursion on Circular allOf/anyOf/oneOf Schemas Causes Fatal Process CrashAlso CWE-674
  • kin-openapi: Unauthenticated panic (DoS) in openapi3filter legacy router via non-canonical/unsupported HTTP method on a static pathSame generic ecosystem
  • kin-openapi spec loader panics on a self-referential additionalProperties $ref (nil-pointer DoS)Same generic ecosystem
  • kin-openapi openapi3filter: nil-pointer panic in ValidateResponse on a response header declared with contentSame generic ecosystem
  • kin-openapi deepObject query decoding repeatedly compiles an invariant regular expressionSame generic ecosystem
  • kin-openapi: ValidationHandler security-requirement bypass via encoded-path operation confusionSame generic ecosystem

Record context

Vulnerability class
Vulnerability
EPSS
Not reported
CWE IDs
CWE-674
Source
CVE List V5
Source checked
Oct 15, 2026
References
5 linked sources
Open source record