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.
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Mon, 09 Nov 2026 21:45:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | 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. | |
| Title | ModSecurity: removeComments Transformation Fails to Strip Adjacent Comments, Enabling WAF Rule Bypass | |
| Weaknesses | CWE-670 | |
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| Metrics |
cvssV3_1
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Status: PUBLISHED
Assigner: GitHub_M
Published:
Updated: 2026-11-09T21:37:00.048Z
Reserved: 2026-10-01T19:04:39.706Z
Link: CVE-2026-104259
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