CVE-2026-61812
ModSecurity: HTML decoder missing entities, leading to evasion
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, 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.
Fixes and workarounds
No remediation reported in collected sources.
Missing remediation information is not evidence that no patch exists.
Affected products and versions
| Product | Versions | Authority |
|---|---|---|
| ModSecurity owasp-modsecurity |
< 2.9.15 (affected) >= 3.0.0, < 3.0.17 (affected) |
CNA: GitHub_M |
Version ranges are source assertions. Check the vendor advisory and your installed configuration before determining exposure.
CVSS assessments
| Version / score | Vector | Authority |
|---|---|---|
| 4.0 / 6.3 medium |
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 | CNA: GitHub_M |
Exploit evidence
No exploit evidence in collected sources. This is not proof of no exploitation.
References
- https://github.com/owasp-modsecurity/ModSecurity/security/advisories/GHSA-cxqf-vgrr-xxrvCNA: GitHub_M · x_refsource_CONFIRM
- https://github.com/owasp-modsecurity/ModSecurity/commit/6353be7b09ff222d29a7491c26307d293b00d56fCNA: GitHub_M · x_refsource_MISC
- https://github.com/owasp-modsecurity/ModSecurity/commit/77be8039d734d36ec291d8fbda9e69326ae44755CNA: GitHub_M · x_refsource_MISC
- https://github.com/owasp-modsecurity/ModSecurity/releases/tag/v2.9.15CNA: GitHub_M · x_refsource_MISC
- https://github.com/owasp-modsecurity/ModSecurity/releases/tag/v3.0.17CNA: GitHub_M · x_refsource_MISC
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