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24Track

ModSecurity: RFC 2231 `filename*` Parameter Bypasses Multipart Filename Rules on RFC-Compliant…

owasp-modsecurity ModSecurity · CVE-2026-104269 GHSA-5PWW-8RFG-9CRF
0 news outlets3 CERTs and agencies0 research labs

Assessment: Track

SSVC decision points: exploitation poc, automatable yes, technical impact partial, deployment high.

What is it?

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.

Evidence

Official warnings4National CERTs, government cyber security agencies and the vendor’s own advisories

Exploitation

  • Exploit code published (not verified by us)
  • Exploited in the wild (confirmed by a source)
  • Listed as known exploited (CISA KEV)
CVSS
8.6
EPSS
0.6%
First seen
1 d ago
Status
confirmed

All owasp-modsecurity vulnerabilities