CVE-2026-104269
ModSecurity: RFC 2231 `filename*` Parameter Bypasses Multipart Filename Rules on RFC-Compliant Backends (Go, Python, Node, Java)
ModSecurity is an open source, cross platform web application firewall (WAF) engine for Apache, IIS and Nginx. From 3.0.0 until 3.0.17, ModSecurity's multipart parser does not apply the RFC 2231 filename* parameter precedence used by common Go, Python, Node.js, and Java application parsers. A Content-Disposition header can provide a benign filename parameter for ModSecurity and a different encoded filename* value that the backend prefers, causing MULTIPART_FILENAME rules and the application to make security decisions on different names. Applications that use the backend-selected name for storage, extension checks, or content-type inference can therefore receive a filename that bypassed WAF inspection. PHP's native multipart parser is not affected by this discrepancy. This issue is fixed in version 3.0.17.
Fixes and workarounds
No remediation reported in collected sources.
Missing remediation information is not evidence that no patch exists.
Affected products and versions
| Product | Versions | Authority |
|---|---|---|
| ModSecurity owasp-modsecurity |
>= 3.0.0, < 3.0.17 (affected) | CNA: GitHub_M |
Version ranges are source assertions. Check the vendor advisory and your installed configuration before determining exposure.
CVSS assessments
| Version / score | Vector | Authority |
|---|---|---|
| 3.1 / 8.6 high |
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:N | CNA: GitHub_M |
Exploit evidence
No exploit evidence in collected sources. This is not proof of no exploitation.
References
- https://github.com/owasp-modsecurity/ModSecurity/security/advisories/GHSA-5pww-8rfg-9crfCNA: GitHub_M · x_refsource_CONFIRM
- https://github.com/owasp-modsecurity/ModSecurity/commit/463db0c840fa27bfba095b0406a63004a12884b0CNA: GitHub_M · x_refsource_MISC
- https://github.com/owasp-modsecurity/ModSecurity/commit/c6bd53d2dd96766b3afdc35d9929ebb20925d13dCNA: GitHub_M · x_refsource_MISC
- https://github.com/owasp-modsecurity/ModSecurity/releases/tag/v2.9.15CNA: GitHub_M · x_refsource_MISC
- https://github.com/owasp-modsecurity/ModSecurity/releases/tag/v3.0.17CNA: GitHub_M · x_refsource_MISC
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