Vulnerability in fail2ban (ALPINE-CVE-2021-32749)

Summary

vulnerability in fail2ban (ALPINE-CVE-2021-32749). Successful exploitation can lead to full system takeover. Exploitable via ``mail``. Mitigation: upgrade to `0.11.2-r1` or later.

AI summary snake-internal / snake-material-v2

A vulnerability tracked as **ALPINE-CVE-2021-32749** has been found in fail2ban. Attackers can target a specific entry point like ``mail`` over the network to misuse the product. Successful exploitation can lead to full system takeover. CVSS score: ?/10. What to do: upgrade fail2ban to **0.11.2-r1** or later. If unsure, ask your IT team or search "fail2ban ALPINE-CVE-2021-32749" on the vendor's site.

ALPINE-CVE-2021-32749 (fail2ban) — Attack vector: remote (network-reachable) / unauthenticated / no user interaction Attack surface: `mail` Patched: `0.11.2-r1` — 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 fail2ban. Attackers reach the vulnerable code path via ``mail`` without authentication.

📍 Affected scope

fail2ban — . Attack surface: `mail`.

🔥 Severity

Severity: ?. Successful exploitation can lead to full system takeover

🔧 How to fix

Update to **0.11.2-r1**.

🛡️ 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 'fail2ban' .` against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.

Response Actions (7 steps)

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

1
Identify exposure identify
```
grep -r 'fail2ban' . | 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 `fail2ban` を grep し、稼働しているサービス・バージョンを把握する。
6
Apply patch patch
```
Upgrade fail2ban to 0.11.2-r1
```
ステージング環境で 0.11.2-r1 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と、Step 3 で見つけた異常検知の続報チェックを含めること。
7
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 Step 3 と同じログクエリでアラート再発が無いか継続監視。