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

Quick assessment

Affected
sensiolabs symfony
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

以下是对该漏洞描述信息的中文翻译： 在 Symfony YAML 组件中，低于 5.4.54、6.4.45、7.4.18 和 8.1.6 版本的受影响版本存在安全漏洞。 方法在处理内联集合（inline collection）中的每一个 和 时，会通过递归调用 和 进行词法分析，而未能像解析器其余部分那样，通过 限制进入嵌套层级。这导致由深层嵌套内联集合（如 ）构成的 YAML 文档在词法分析过程中耗尽栈空间：根据 PHP 版本及其栈设置，进程可能会崩溃，或请求以致命错误（fatal error）结束。 任何解析不

CVSS 8.7 · High EPSS 0.51% · P42

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

Affected Version Matrix 4

VendorProduct Version RangeStatus
sensiolabs symfony < v5.4.54 affected
v6.0.0-BETA1< v6.4.45 affected
v7.0.0-BETA1< v7.4.18 affected
v8.0.0-BETA1< v8.1.6 affected
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I. Basic Information for CVE-2026-109413

Vulnerability Information
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Vulnerability Title
Symfony: Unbounded Recursion in the YAML Inline Lexer Lets a Single Document Crash the Process
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
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
Source: CVE Program / CVE List V5
Vulnerability Type
未经控制的递归
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
sensiolabs symfony 0 ~ v5.4.54 -

II. Public POCs for CVE-2026-109413

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III. Intelligence Information for CVE-2026-109413

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Patches & Fixes for CVE-2026-109413 (1)

Vendor Advisories for CVE-2026-109413 (1)

Other References for CVE-2026-109413 (1)

Same Patch Batch · sensiolabs · 2026-10-15 · 3 CVEs total

CVE-2026-108082 8.7 HIGH Symfony: ReDoS in HeaderUtils::split() Reachable Through the Cache-Control Request Header
CVE-2026-109449 8.7 HIGH Symfony: Unbounded Nesting in the Expression Parser Lets Untrusted Expressions Crash the P

IV. Related Vulnerabilities

Same product: symfony
Same vendor: sensiolabs
Same weakness: CWE-674

V. Comments for CVE-2026-109413

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