CVE-2026-30923 HIGH

CVE-2026-30923: libModSecurity3 denial of service via segfault when using t:hexDecode on single-character query strings

Vendor Owasp-Modsecurity
Product ModSecurity
Weakness CWE-125
Published May 5, 2026
Last update May 5, 2026
View on NVD All CVEs

CVSS base score

8.2/10
Attack vector Network
Attack complexity Low
Privileges required None
User interaction None
Confidentiality —
Integrity —

CVSS vector

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

What the vulnerability does

01Description

ModSecurity is an open source, cross platform web application firewall (WAF) engine for Apache, IIS and Nginx. Libmodsecurity is one component of the ModSecurity v3 project. A segmentation fault occurs when a rule using the t:hexDecode transformation inspects a query string parameter containing a single character. An attacker can exploit this to crash worker processes, causing a denial of service. Service resumes once the attack stops as worker processes recover from the segfault. All versions before 3.0.15 of libModSecurity3 are affected. This has been patched in version 3.0.15.

Key dates

02Disclosure timeline

May 5, 2026 CVE published
May 5, 2026 Record updated