ModSecurity: removeComments Transformation Fails to Strip Adjacent Comments, Enabling WAF Rule Bypass

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-104259
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-11-09 22:18:22 UTC
Updated2026-11-10 19:17:41 UTC
DescriptionModSecurity 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.

Risk And Classification

Primary CVSS: v3.1 5.4 MEDIUM from [email protected]

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

EPSS: 0.002230000 probability, percentile 0.129620000 (date 2026-11-10)

Problem Types: CWE-670 | CWE-670 CWE-670: Always-Incorrect Control Flow Implementation

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary5.4MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:N
3.1CNADECLARED5.4MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:N

CVSS v3.1 Breakdown

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

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Owasp-modsecurity ModSecurity affected < 2.9.15 Not specified
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/security/advisories/GHSA-qrch-p... [email protected] github.com
github.com/owasp-modsecurity/ModSecurity/commit/264f348ae1823cb71cead365... [email protected] github.com
github.com/owasp-modsecurity/ModSecurity/commit/49a65f471d3130b91f7fff9b... [email protected] github.com
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NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

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