CVE-2026-30923CWE-125

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

High · published May 5, 2026

CVSS v4.0
8.2
EPSS
1%
Percentile
43.0
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v4.0
8.2 · HIGH
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
EPSS
0.00515 · 43.0th percentile
Weakness
CWE-125 · Out-of-bounds Read
Published
2026-05-05T18:46Z
EPSS history
Timeline
  • 05 MAY 18:46Z
    libModSecurity3 denial of service via segfault when using t:hexDecode on single-character query strings
    cvelistv5