owasp-modsecurity ModSecurity up to 3.0.16 Multipart Parser input validation

Summaryinfo

A vulnerability, which was classified as problematic, has been found in owasp-modsecurity ModSecurity up to 3.0.16. Affected by this issue is some unknown functionality of the component Multipart Parser. This manipulation causes input validation. The identification of this vulnerability is CVE-2026-104269. It is possible to initiate the attack remotely. There is no exploit available. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability has been found in owasp-modsecurity ModSecurity up to 3.0.16 and classified as problematic. Affected by this vulnerability is an unknown functionality of the component Multipart Parser. The manipulation with an unknown input leads to a input validation vulnerability. The CWE definition for the vulnerability is CWE-20. The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly. As an impact it is known to affect integrity. The summary by CVE is:

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.

The advisory is shared at github.com. This vulnerability is known as CVE-2026-104269 since 10/01/2026. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. Neither technical details nor an exploit are publicly available.

Upgrading to version 3.0.17 eliminates this vulnerability.

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Productinfo

Vendor

• owasp-modsecurity

Name

• ModSecurity

Version

• 3.0.0
• 3.0.1
• 3.0.2
• 3.0.3
• 3.0.4
• 3.0.5
• 3.0.6
• 3.0.7
• 3.0.8
• 3.0.9
• 3.0.10
• 3.0.11
• 3.0.12
• 3.0.13
• 3.0.14
• 3.0.15
• 3.0.16

Website

• Product: https://github.com/owasp-modsecurity/ModSecurity/

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