Skip to content
Fencer Vulns
high 7.5

CVE-2026-30923 json

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

published 2026-05-05 6 mo ago modified 2026-09-08 2 mo ago also BIT-modsecurity-2026-30923 , BIT-modsecurity2-2026-30923 , EUVD-2026-27422 , GHSA-qrjc-3jpc-3h2g

cvss
7.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 38%
public exploits
0
none known

Summary

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.

Patch / fix

  • bitnami modsecurity 3.0.15
  • owasp libmodsecurity 3.0.15
  • owasp modsecurity 3.0.15
  • owasp owasp_modsecurity 3.0.15
  • trustwave modsecurity 3.0.15
  • modsecurity Debian 12 3.0.9-1+deb12u2
  • modsecurity Debian 13 3.0.14-1+deb13u1
  • modsecurity Debian 14 3.0.15-1

debian advisories DEBIAN-CVE-2026-30923

  • modsecurity openSUSE Tumbleweed 3.0.15-1.1

opensuse advisories openSUSE-SU-2026:10732-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-30923 updated cvss 7.5

libModSecurity3: ModSecurity: ModSecurity: Denial of Service via crafted query string parameter in t:hexDecode transformation

  • Red Hat Enterprise Linux 7 mod_security, mod_security-mlogc Red Hat Enterprise Linux 8 mod_security, mod_security-mlogc Red Hat Enterprise Linux 9 mod_security, mod_security-mlogc
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
Proof of concept is public
Automatable
yes
Technical impact
partial
Assessed
6 mo ago

Exploit prediction

0.43% chance of exploitation in the next 30 days, higher than 38% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/owasp-modsecurity/ModSecurity/security/advisories/GHSA-qrjc-3jpc-3h2g referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 4.0 8.2 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
CNA 4.0 8.2 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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
NVD 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected packages

ecosystem package affected fixed in
bitnami modsecurity
>=3.0.0, <3.0.15
3.0.15

Affected products

  • owasp-modsecurity ModSecurity

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.