Vulnerability in io.netty:netty-codec (CVE-2021-37136, CVSS 7.5)

Summary

Vulnerability in io.netty:netty-codec (CVE-2021-37136). Risk of unauthorized operations or information disclosure. Exploitable via Bzip2Decoder. Mitigation: upgrade to 4.1.68.Final or later.

Original description

The description as published by the source.

Impact

The Bzip2 decompression decoder function doesn't allow setting size restrictions on the decompressed output data (which affects the allocation size used during decompression).

All users of Bzip2Decoder are affected. The malicious input can trigger an OOME and so a DoS attack

Workarounds

No workarounds other than not using the Bzip2Decoder

References

Relevant code areas:

https://github.com/netty/netty/blob/netty-4.1.67.Final/codec/src/main/java/io/netty/handler/codec/compression/Bzip2Decoder.java#L80
https://github.com/netty/netty/blob/netty-4.1.67.Final/codec/src/main/java/io/netty/handler/codec/compression/Bzip2Decoder.java#L294
https://github.com/netty/netty/blob/netty-4.1.67.Final/codec/src/main/java/io/netty/handler/codec/compression/Bzip2Decoder.java#L305

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-2021-37136 has been found in io.netty:netty-codec.
Attackers can target a specific entry point like Bzip2Decoder over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 7.5/10.
What to do: upgrade io.netty:netty-codec to 4.1.68.Final or later.
If unsure, ask your IT team or search "io.netty:netty-codec CVE-2021-37136" on the vendor's site.

CVE-2021-37136 (io.netty:netty-codec) — CWE-400 / CVSS v3 7.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: Bzip2Decoder
Patched: 4.1.68.Final — apply immediately
Workaround: No workarounds other than not using the Bzip2Decoder
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 (CWE-400) exists in io.netty:netty-codec. Attackers reach the vulnerable code path via Bzip2Decoder without authentication.

📍 Affected scope

Check the vendor advisory for the affected versions of io.netty:netty-codec. Attack surface: Bzip2Decoder.

🔥 Severity

Severity: High (CVSS 7.5/10). Risk of unauthorized operations or information disclosure.

🔧 How to fix

Update to 4.1.68.Final.

🛡️ Workaround

Workaround: No workarounds other than not using the Bzip2Decoder

🔍 Detection

Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Audit SBOM/dependencies to find affected services.

Response actions

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

1
Identify exposure identify
```
Audit SBOM/dependencies for affected components.
```
資産台帳・SBOM・依存マニフェストで io.netty:netty-codec を使っているサービスとバージョンを洗い出す。
2
Apply temporary workaround mitigate
```
No workarounds other than not using the `Bzip2Decoder`
```
パッチが適用されるまでの応急処置として、No workarounds other than not using the Bzip2Decoder を実施。回避策の副作用 (機能低下) を確認した上で。
3
Apply patch patch
```
Upgrade io.netty:netty-codec to 4.1.68.Final
```
ステージング環境で 4.1.68.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を含めること。
4
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。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。

Affected packages

Maven io.netty:netty-codec

[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"4.1.68.Final"}]}]

Maven org.jboss.netty:netty

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

Maven io.netty:netty

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

Fix status by distribution

Fixed packages published by each distribution for this CVE

Ubuntu UBUNTU-CVE-2021-37136 netty