# CVE-2026-30923: modsecurity: ModSecurity is an open source, cross platform web application firewall (WAF) engine for Apache, IIS and Nginx

CVE-2026-30923 is fixed in modsecurity on 1 platform, first by DEBIAN-CVE-2026-30923, released May 15, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-30923
- Priority: High
- CVSS: 7.5 (high)
- EPSS: 0.0044
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: May 5, 2026

## 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | modsecurity Debian 12.15 (bookworm) | 3.0.9-1+deb12u2 | [DEBIAN-CVE-2026-30923](https://patchblox.com/security/data/fix/linux/debian-cve-2026-30923.md) | May 15, 2026 |
| Linux | modsecurity Debian 13.5 (trixie) | 3.0.14-1+deb13u1 | [DEBIAN-CVE-2026-30923](https://patchblox.com/security/data/fix/linux/debian-cve-2026-30923.md) | May 15, 2026 |
| Linux | modsecurity Debian 14 | 3.0.15-1 | [DEBIAN-CVE-2026-30923](https://patchblox.com/security/data/fix/linux/debian-cve-2026-30923.md) | May 15, 2026 |

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Data as of 2026-11-08T19:12:23Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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