Vulnerability in undertow (UBUNTU-CVE-2025-12543)

Summary

vulnerability in undertow (UBUNTU-CVE-2025-12543). Confidential information can be exposed externally. Exploitable via `Host header`. Mitigation: upgrade to `1.3.16-1ubuntu0.1~esm1` or later.

AI summary snake-internal / snake-material-v2

A vulnerability tracked as **UBUNTU-CVE-2025-12543** has been found in undertow. Attackers can target a specific entry point like `Host header` over the network to misuse the product. Confidential information can be exposed externally. CVSS score: ?/10. What to do: upgrade undertow to **1.3.16-1ubuntu0.1~esm1** or later. If unsure, ask your IT team or search "undertow UBUNTU-CVE-2025-12543" on the vendor's site.

UBUNTU-CVE-2025-12543 (undertow) — Attack vector: remote (network-reachable) / unauthenticated Attack surface: Host header Patched: `1.3.16-1ubuntu0.1~esm1` — 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 undertow. Attackers reach the vulnerable code path via `Host header` without authentication.

📍 Affected scope

undertow — . Attack surface: Host header.

🔥 Severity

Severity: ?. Confidential information can be exposed externally

🔧 How to fix

Update to **1.3.16-1ubuntu0.1~esm1**.

🛡️ 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 'undertow' .` 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 'undertow' . | 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 `undertow` 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 undertow to 1.3.16-1ubuntu0.1~esm1
```
ステージング環境で 1.3.16-1ubuntu0.1~esm1 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:16.04:LTS undertow

[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.3.16-1ubuntu0.1~esm1"}]}]

Ubuntu:Pro:18.04:LTS undertow

[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.4.23-3ubuntu0.1~esm1"}]}]

Ubuntu:Pro:20.04:LTS undertow

[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.0.29-1ubuntu0.1~esm1"}]}]

Ubuntu:Pro:22.04:LTS undertow

[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.2.16-1ubuntu0.1~esm1"}]}]

Ubuntu:Pro:24.04:LTS undertow

[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.3.8-2ubuntu0.1~esm1"}]}]

Ubuntu:25.10 undertow

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

Ubuntu:26.04:LTS undertow

[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.3.20-1ubuntu1"}]}]

References

advisory https://ubuntu.com/security/notices/USN-8144-1
report https://ubuntu.com/security/CVE-2025-12543
report https://www.cve.org/CVERecord?id=CVE-2025-12543
report https://access.redhat.com/security/cve/CVE-2025-12543
report https://bugzilla.redhat.com/show_bug.cgi?id=2408784
report https://github.com/undertow-io/undertow/pull/1857
report https://github.com/undertow-io/undertow/pull/1882
report https://github.com/undertow-io/undertow/pull/1860
report https://github.com/undertow-io/undertow/pull/1894