ModSecurity: HTML decoder missing entities, leading to evasion

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-61812
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-11-09 22:18:53 UTC
Updated2026-11-12 22:18:51 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, t:htmlEntityDecode recognizes only a small subset of named HTML entities, so rules that depend on the transformation can inspect different bytes than a browser or backend. Attackers can encode ASCII separators and operators with unhandled entity names, including aliases, to bypass rules that depend on the transformation. The v3 decoder also accepts prefix matches instead of requiring an exact entity-token length, which can transform invalid longer names into different bytes. This issue is fixed in versions 2.9.15 and 3.0.17.

Risk And Classification

Primary CVSS: v4.0 6.3 MEDIUM from [email protected]

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Problem Types: CWE-172 | CWE-180 | CWE-172 CWE-172: Encoding Error | CWE-180 CWE-180: Incorrect Behavior Order: Validate Before Canonicalize

VersionSourceTypeScoreSeverityVector
4.0[email protected]Secondary6.3MEDIUMCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:L/SA:N/E:X/C...
4.0CNADECLARED6.3MEDIUMCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:L/SA:N

CVSS v4.0 Breakdown

Attack Vector
Network
Attack Complexity
Low
Attack Requirements
Present
Privileges Required
None
User Interaction
None
Confidentiality
None
Integrity
Low
Availability
None
Sub Conf.
None
Sub Integrity
Low
Sub Availability
None

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

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-cxqf-v... [email protected] github.com
github.com/owasp-modsecurity/ModSecurity/commit/77be8039d734d36ec291d8fb... [email protected] github.com
github.com/owasp-modsecurity/ModSecurity/commit/6353be7b09ff222d29a7491c... [email protected] github.com
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