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CVE-2026-109413Suited to automated attack · CISA

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

CVSS score

8.7

EPSS probability

—

Risk score

0.9

Published

6 h ago

OverviewPublic Exploits (0)NewsroomVulnerability Timeline
Official patch verified

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Vulnerability description

CVE AI research

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DayBreach AI Explanation

Verified against sources

CVE-2026-109413: Unbounded Recursion Vulnerability in Symfony YAML

Sources read

1

Source agreement

Tam uyum

Evidence confidence

%55

Short explanation

A flaw in the Symfony YAML component causes unbounded recursion in the YAML inline lexer, allowing a single request to crash the process or trigger a fatal error.

Why does it matter?

A single unauthenticated request can crash the target service when parsing untrusted YAML data.

What should be done?

  • Follow vendor security advisories
  • Restrict endpoint accept formats
  • Exercise caution when processing untrusted YAML data
Chain of evidence and sources2 verified claims

Symfony YAML bileşeninde Yaml\Parser::lexInlineStructure() fonksiyonu maxNestingLevel sınırına girmeden özyineleme yapar.

S0 · daybreach-canonicalS1 · nvd

Derinlemesine iç içe geçmiş satır içi koleksiyonlar yığını tüketerek sürecin çökmesine neden olur.

S0 · daybreach-canonicalS1 · nvd
Show the technical text from the sources

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 vector: 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

CWE: CWE-674

Explanation produced with the local gemini-flash-lite-latest model. Numerical metrics and the KEV, patch and exploit statuses are not determined by AI.

IMPACT: Affected Products and Software

Affected Products

The following products are affected by CVE-2026-109413 vulnerability. Where our threat engine knows the exact affected versions, they are listed below.

IDVENDORPRODUCTACTION
1sensiolabssymfony View
Total affected vendors: 1|Products: 1

RED HAT CSAF/VEX: Product Impact Check

Red Hat has not yet published a CSAF/VEX impact record for this CVE. This does not mean “not affected”.

SCORING: CVSS from Multiple Sources

CVSS Scores

The Common Vulnerability Scoring System is a standardised framework for assessing the severity of vulnerabilities in software and systems. We collect and display CVSS scores from several sources for each CVE.

SCOREVERSIONSEVERITYVECTORSOURCE
8.7CVSS V40HIGHCVSS: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:XNVD
8.7CVSS V4_0HIGHCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:NCVE CNA

Patch and Remediation Guide

Solution & Remediation Advisory

Patch verified

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cvelist

CNA çözüm referansı

Open source
reference

Yama veya çözüm referansı

Open source
Confirm the affected product and version against the source evidence above.
Restrict access to internet-facing services and apply network segmentation.
Apply the official update named in the evidence only to the matching product and version.
Monitor server logs and network endpoints for signs of anomalous execution.

Public exploit and active exploitation status

Verified exploit intelligence

No verified public PoC, exploit repository or Metasploit module has been found for this CVE yet.

Weakness Classification and Attack Patterns (CWE & CAPEC)

CWE - Common Weakness Enumeration

While CVE identifies specific instances of vulnerabilities, CWE categorises the common flaws or weaknesses that can lead to vulnerabilities. CVE-2026-109413 is associated with the following CWEs:

CWE-674: Common Weakness Enumeration Entry CWE-674

Common Attack Pattern Enumeration and Classification (CAPEC)

Common Attack Pattern Enumeration and Classification (CAPEC) stores attack patterns, which are descriptions of the common attributes and approaches employed by adversaries to exploit the CVE-2026-109413 weaknesses.

CAPEC-66: SQL InjectionCAPEC-126: Path TraversalCAPEC-28: OS Command Injection

Attack Vector and Accessibility

ExposureAğ üzerinden
PermissionsGerekmiyor
UserGerekmiyor

Official Sources and Advisories

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

CVSS Vector Radar Chart

8.7 / 10
Attack VectorNetworkComplexityLowPrivilegesNoneUser Interact.NoneConfidentialityLowIntegrityNoneAvailabilityHigh

Vulnerability Scoring Details

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
Attack VectorNetwork
Attack ComplexityLow
Privileges RequiredNone required
User InteractionNone required
Confidentiality (Gizlilik)Low
Integrity (Bütünlük)None
Availability (Erişilebilirlik)High

Yama doğrulandı

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Weakness Type (CWE & CAPEC)

CWE-674

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