Vulnerability in dnsmasq (UBUNTU-CVE-2026-4892)

Summary

vulnerability in dnsmasq (UBUNTU-CVE-2026-4892). Successful exploitation can lead to full system takeover. Mitigation: upgrade to `2.68-1ubuntu0.2+esm5` or later.

AI summary snake-internal / snake-material-v2

A vulnerability tracked as **UBUNTU-CVE-2026-4892** has been found in dnsmasq. Successful exploitation can lead to full system takeover. CVSS score: ?/10. What to do: upgrade dnsmasq to **2.68-1ubuntu0.2+esm5** or later. If unsure, ask your IT team or search "dnsmasq UBUNTU-CVE-2026-4892" on the vendor's site.

UBUNTU-CVE-2026-4892 (dnsmasq) — Attack vector: local / unauthenticated / no user interaction Patched: `2.68-1ubuntu0.2+esm5` — 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 dnsmasq.

📍 Affected scope

dnsmasq — .

🔥 Severity

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

🔧 How to fix

Update to **2.68-1ubuntu0.2+esm5**.

🛡️ 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 'dnsmasq' .` 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 'dnsmasq' . | 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 `dnsmasq` 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 dnsmasq to 2.68-1ubuntu0.2+esm5
```
ステージング環境で 2.68-1ubuntu0.2+esm5 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。

Affected packages

Ubuntu:Pro:14.04:LTS dnsmasq

[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.68-1ubuntu0.2+esm5"}]}]

Ubuntu:Pro:16.04:LTS dnsmasq

[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.90-0ubuntu0.16.04.1+esm3"}]}]

Ubuntu:Pro:18.04:LTS dnsmasq

[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.90-0ubuntu0.18.04.1+esm3"}]}]

Ubuntu:20.04:LTS dnsmasq

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

Ubuntu:22.04:LTS dnsmasq

[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.90-0ubuntu0.22.04.3"}]}]

Ubuntu:24.04:LTS dnsmasq

[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.90-2ubuntu0.3"}]}]

Ubuntu:25.10 dnsmasq

[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.91-1ubuntu0.2"}]}]

Ubuntu:26.04 dnsmasq

[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.92-1ubuntu0.2"}]}]

Ubuntu:Pro:20.04:LTS dnsmasq

[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.90-0ubuntu0.20.04.1+esm2"}]}]

References

advisory https://ubuntu.com/security/notices/USN-8268-1
report https://ubuntu.com/security/CVE-2026-4892
report https://www.cve.org/CVERecord?id=CVE-2026-4892