Encoding Error in ModSecurity - CVE-2026-61812
Published: November 4, 2026
Vulnerability identifier: #VU159010
CSH Severity: Medium
CVSS v4: 6.9 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-61812
CWE-ID: CWE-172
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to bypass security rules that rely on HTML entity decoding to normalize input.
The vulnerability exists due to incomplete decoding of named HTML entities in the t:htmlEntityDecode transformation when processing request input. A remote attacker can encode payload characters using unrecognized entities, such as q=javascript:execute_my_code();, to evade rules that would block the decoded payload.
Affected software
ModSecurity
How to mitigate CVE-2026-61812
Install security update from vendor's website.
ModSecurity - addressed in versions 2.9.15, 3.0.17