Vulnerability in modsecurity (DEBIAN-CVE-2026-30923)

Summary

Vulnerability in modsecurity (DEBIAN-CVE-2026-30923). Risk of unauthorized operations or information disclosure. Mitigation: upgrade to 3.0.15-1 or later.

Original description

The description as published by the source.

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.

Source: OSV.dev (Open Source Vulnerabilities) OSV

Auto-generated summary

Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.

A vulnerability tracked as DEBIAN-CVE-2026-30923 has been found in modsecurity.
Risk of unauthorized operations or information disclosure.
What to do: upgrade modsecurity to 3.0.15-1 or later.
If unsure, ask your IT team or search "modsecurity DEBIAN-CVE-2026-30923" on the vendor's site.

DEBIAN-CVE-2026-30923 (modsecurity)
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Patched: 3.0.15-1 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.

❓ What is the problem

A vulnerability (unclassified) exists in modsecurity.

📍 Affected scope

Check the vendor advisory for the affected versions of modsecurity.

🔥 Severity

Severity: ?. Risk of unauthorized operations or information disclosure.

🔧 How to fix

Update to 3.0.15-1.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'modsecurity' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.

Response actions

Concrete steps and command examples for SOC/SRE teams to execute in order

1
Identify exposure identify
```
grep -r 'modsecurity' . | grep -v node_modules
```
リポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で modsecurity を grep し、稼働しているサービス・バージョンを把握する。
2
Apply patch patch
```
Upgrade modsecurity to 3.0.15-1
```
ステージング環境で 3.0.15-1 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
3
Post-deployment verification verify
```
Confirm patched version is live in production
```
パッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。

Affected packages

Debian:11 modsecurity

[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]

Debian:12 modsecurity

[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"3.0.9-1+deb12u2"}]}]

Debian:13 modsecurity

[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"3.0.14-1+deb13u1"}]}]

Debian:14 modsecurity

[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"3.0.15-1"}]}]

References

advisory security-tracker.debian.org