Out-of-Bounds Read in modsecurity2 (CVE-2026-30923)
Summary
Vulnerability in modsecurity2 (CVE-2026-30923). Risk of unauthorized operations or information disclosure. Mitigation: upgrade to 3.0.15 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) NVD GitHub Advisory 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 CVE-2026-30923 has been found in modsecurity2.
Risk of unauthorized operations or information disclosure. CVSS score: 7.5/10.
What to do: upgrade modsecurity2 to 3.0.15 or later.
If unsure, ask your IT team or search "modsecurity2 CVE-2026-30923" on the vendor's site.
CVE-2026-30923 (modsecurity2) — CWE-125 / CVSS v3 7.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Patched: 3.0.15 — 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.
Out-of-bounds read (CWE-125) exists in modsecurity2.
Check the vendor advisory for the affected versions of modsecurity2.
Severity: High (CVSS 7.5/10). Risk of unauthorized operations or information disclosure.
Update to 3.0.15.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'modsecurity2' . 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
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1Identify exposure identify
grep -r 'modsecurity2' . | 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
modsecurity2を grep し、稼働しているサービス・バージョンを把握する。 -
2Apply patch patch
Upgrade modsecurity2 to 3.0.15ステージング環境で 3.0.15 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。
-
3Post-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
Fix status by distribution
Fixed packages published by each distribution for this CVE
- Debian DEBIAN-CVE-2026-30923 modsecurity
- Ubuntu UBUNTU-CVE-2026-30923 modsecurity
References
- advisory github.com
- advisory nvd.nist.gov
- advisory github.com
- web github.com