Vulnerability in netty (UBUNTU-CVE-2021-21295)

Summary

vulnerability in netty (UBUNTU-CVE-2021-21295). Data can be tampered with by attackers. Exploitable via ``Http2MultiplexHandler``. Mitigation: upgrade to `4.1.60.Final` or later.

AI summary snake-internal / snake-material-v2

A vulnerability tracked as **UBUNTU-CVE-2021-21295** has been found in netty. Attackers can target a specific entry point like ``Http2MultiplexHandler`` over the network to misuse the product. Data can be tampered with by attackers. CVSS score: ?/10. What to do: upgrade netty to **4.1.60.Final** or later. If unsure, ask your IT team or search "netty UBUNTU-CVE-2021-21295" on the vendor's site.

UBUNTU-CVE-2021-21295 (netty) — Attack vector: remote (network-reachable) / unauthenticated / no user interaction Attack surface: `Http2MultiplexHandler` / `HttpRequest` / `HttpContent` / `HTTP2MultiplexCodec` Patched: `4.1.60.Final` — 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 netty. Attackers reach the vulnerable code path via ``Http2MultiplexHandler`` without authentication.

📍 Affected scope

netty — . Attack surface: `Http2MultiplexHandler` / `HttpRequest` / `HttpContent` / `HTTP2MultiplexCodec`.

🔥 Severity

Severity: ?. Data can be tampered with by attackers

🔧 How to fix

Update to **4.1.60.Final**.

🛡️ 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 'netty' .` 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 'netty' . | 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 `netty` 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 netty to 4.1.60.Final
```
ステージング環境で 4.1.60.Final 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 netty

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

Ubuntu:Pro:16.04:LTS netty

[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1:4.0.34-1ubuntu0.1~esm1"}]}]

Ubuntu:Pro:18.04:LTS netty

[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1:4.1.7-4ubuntu0.1+esm2"}]}]

Ubuntu:Pro:20.04:LTS netty

[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1:4.1.45-1ubuntu0.1~esm1"}]}]

Ubuntu:22.04:LTS netty

[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1:4.1.48-4+deb11u1build0.22.04.1"}]}]