ModSecurity: RFC 2231 `filename*` Parameter Bypasses Multipart Filename Rules on RFC-Compliant Backends (Go, Python, Node, Java)

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-104269
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-11-05 16:17:29 UTC
Updated2026-11-05 16:17:29 UTC
DescriptionModSecurity 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.

Risk And Classification

Primary CVSS: v3.1 8.6 HIGH from [email protected]

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:N

Problem Types: CWE-436 | CWE-436 CWE-436: Interpretation Conflict

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary8.6HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:N
3.1CNADECLARED8.6HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Changed
Confidentiality
None
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:N

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Owasp-modsecurity ModSecurity affected >= 3.0.0, < 3.0.17 Not specified

References

ReferenceSourceLinkTags
github.com/owasp-modsecurity/ModSecurity/releases/tag/v3.0.17 [email protected] github.com
github.com/owasp-modsecurity/ModSecurity/releases/tag/v2.9.15 [email protected] github.com
github.com/owasp-modsecurity/ModSecurity/commit/463db0c840fa27bfba095b04... [email protected] github.com
github.com/owasp-modsecurity/ModSecurity/security/advisories/GHSA-5pww-8... [email protected] github.com
github.com/owasp-modsecurity/ModSecurity/commit/c6bd53d2dd96766b3afdc35d... [email protected] github.com
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