TI-2026-23748 Aliases CVE-2026-30923

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

HIGH 75CWE-125Published 2026-05-05 · Updated 2026-05-05

Key facts

Attack vector: Network
Privileges required: None
User interaction: None
Attack complexity: Low
Attack requirements: Present
Impact type: Denial of service
Confidentiality · integrity · availability: None · None · High
Fix status: Fixed

Attack profile from CVSS 4.0 · CNA. Fix status from CNA. Impact type from CWE-125 and the CVSS impact.

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.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV

EPSS 0.00435 38th percentileScored 2026-11-07

Public exploit Yes 1 exploit referenceTagged by NVD

Fix Fixed ModSecurity (owasp-modsecurity): 3.0.15

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: Poc
Automatable: Yes
Technical impact: Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
owasp-modsecurity	ModSecurity	before 3.0.15	3.0.15	Patch available	CNA

ModSecurity Vendorowasp-modsecurity Affected before 3.0.15 Fixed in 3.0.15 Patch available CNA

CPE configurations NVD · 1

CPE	Versions	Role	Vendor
cpe:2.3:a:owasp:modsecurity::::::::	before 3.0.15	Vulnerable	owasp-modsecurity

cpe:2.3:a:owasp:modsecurity:*:*:*:*:*:*:*:* Versions before 3.0.15 Vulnerable ·owasp-modsecurity

Remediation

Fix · CNA ModSecurity (owasp-modsecurity) Fixed in 3.0.15

Vendor assessments

Red Hat

Red Hat rating: Moderate. Red Hat's page for this CVE →

Not affected: 3 products

Red Hat Enterprise Linux 7
Red Hat Enterprise Linux 8
Red Hat Enterprise Linux 9

Timeline

2026-10-02 Threatist record created from CVE-2026-30923

References

Exploit 1

https://github.com/owasp-modsecurity/ModSecurity/security/advisories/GHSA-qrjc-3jpc-3h2g

Patch 1

https://github.com/owasp-modsecurity/ModSecurity/releases/tag/v3.0.15

TI-2026-37865 ModSecurity: Multipart form-data parser silently strips embedded line breaks from… CVSS 3.1HIGH 8.6
TI-2026-30581 ModSecurity: Unsigned integer underflow in @verifySSN / @verifyCPF / @verifySVNR operators CVSS 4.0HIGH 8.2
TI-2025-31022 ModSecurity has possible DoS vulnerability in sanitiseArg action CVSS 3.1HIGH 7.5
TI-2025-34348 ModSecurity's Insufficient Return Value Handling can Lead to XSS and Source Code Disclosure CVSS 4.0MEDIUM 6.9
TI-2024-00942 WAF bypass of the ModSecurity v3 release line CVSS 3.1HIGH 8.6
TI-2023-19686 Trustwave ModSecurity 3.x before 3.0.10 has Inefficient Algorithmic Complexity. CVSS 3.1HIGH 7.5

See all 14 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences