High severity · published May 5, 2026
CVE-2026-30923
libModSecurity3 denial of service via segfault when using t:hexDecode on single-character query strings
7.5
CVSS
0.4%
EPSS
No
On KEV
Description
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
None
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.4% · higher than 38% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
MO
ModSecurity · owasp-modsecurity
< 3.0.15 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-30923
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-30923
Patch
https://github.com/owasp-modsecurity/ModSecurity/releases/tag/v3.0.15
Exploit
https://github.com/owasp-modsecurity/ModSecurity/security/advisories/GHSA-qrjc-3jpc-3h2g
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