OWASP ModSecurity up to 2.9.14/3.0.16 Comment Removal apache2/re_tfns.c msre_fn_removeComments_execute out-of-bounds

Summaryinfo

A vulnerability, which was classified as critical, was found in OWASP ModSecurity up to 2.9.14/3.0.16. This vulnerability affects the function msre_fn_removeComments_execute of the file apache2/re_tfns.c of the component Comment Removal. Executing a manipulation can lead to out-of-bounds. The identification of this vulnerability is CVE-2026-104259. The attack may be launched remotely. There is no exploit available. You should upgrade the affected component.

Detailsinfo

A vulnerability classified as critical was found in OWASP ModSecurity up to 2.9.14/3.0.16. This vulnerability affects the function msre_fn_removeComments_execute of the file apache2/re_tfns.c of the component Comment Removal. The manipulation with an unknown input leads to a out-of-bounds vulnerability. The CWE definition for the vulnerability is CWE-125. The product reads data past the end, or before the beginning, of the intended buffer. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

ModSecurity is an open source, cross platform web application firewall (WAF) engine for Apache, IIS and Nginx. Prior to 2.9.15 and 3.0.17, msre_fn_removeComments_execute in apache2/re_tfns.c and inplace() in src/actions/transformations/remove_comments.cc implement t:removeComments by copying the character immediately after a comment terminator without re-evaluating it. Adjacent comments can therefore leave a later comment in the transformed value, allowing inline-comment obfuscation to bypass rules that depend on comment stripping. When a comment terminator is the final content, the same copy reads one byte beyond the input buffer. This issue is fixed in versions 2.9.15 and 3.0.17.

The advisory is available at github.com. This vulnerability was named CVE-2026-104259 since 10/01/2026. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. Technical details are known, but there is no available exploit.

Upgrading to version 2.9.15 or 3.0.17 eliminates this vulnerability.

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Productinfo

Vendor

• OWASP

Name

• ModSecurity

Version

• 2.9.0
• 2.9.1
• 2.9.2
• 2.9.3
• 2.9.4
• 2.9.5
• 2.9.6
• 2.9.7
• 2.9.8
• 2.9.9
• 2.9.10
• 2.9.11
• 2.9.12
• 2.9.13
• 2.9.14
• 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

License

• open-source

CPE 2.3info

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• 🔒
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CPE 2.2info

• 🔒
• 🔒
• 🔒

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