Out-of-bounds Read in Owasp Modsecurity
CVE-2026-30923
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.
Vulnerability class: Buffer Overflow
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
EPSS exploit prediction
EPSS: 0.005 (42.6th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 43rd percentile — 42.6% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.004 · newest: 0.005 · change: +0.001
Affected products
- Owasp Modsecurity
- Owasp-Modsecurity Modsecurity — versions < 3.0.15
Weakness classification (CWE)
References
- github.com/owasp-modsecurity/ModSecurity/security/advisories/GHSA-qrjc-3jpc-3h2g (Exploit, Vendor Advisory)
- github.com/owasp-modsecurity/ModSecurity/releases/tag/v3.0.15 (Product, Patch)
Frequently asked questions
- What is CVE-2026-30923?
- CVE-2026-30923 is a high-severity vulnerability in Owasp Modsecurity, classified under Out-of-bounds Read. CVSS score: 7.5/10. Published 2026-05-05.
- How severe is CVE-2026-30923?
- High severity. CVSS v3 base score is 7.5 out of 10.