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CVE-2021-21290 medium CVSS 6.2

Vulnerability in Oracle Netty (CVE-2021-21290)

Summary

Vulnerability in Oracle Netty (CVE-2021-21290). Confidential information can be exposed externally.

Original description

The description as published by the source.

Impact

When netty's multipart decoders are used local information disclosure can occur via the local system temporary directory if temporary storing uploads on the disk is enabled.

The CVSSv3.1 score of this vulnerability is calculated to be a 6.2/10

Vulnerability Details

On unix-like systems, the temporary directory is shared between all user. As such, writing to this directory using APIs that do not explicitly set the file/directory permissions can lead to information disclosure. Of note, this does not impact modern MacOS Operating Systems.

The method File.createTempFile on unix-like systems creates a random file, but, by default will create this file with the permissions -rw-r--r--. Thus, if sensitive information is written to this file, other local users can read this information.

This is the case in netty's AbstractDiskHttpData is vulnerable.

https://github.com/netty/netty/blob/e5951d46fc89db507ba7d2968d2ede26378f0b04/codec-http/src/main/java/io/netty/handler/codec/http/multipart/AbstractDiskHttpData.java#L80-L101

AbstractDiskHttpData is used as a part of the DefaultHttpDataFactory class which is used by HttpPostRequestDecoder / HttpPostMultiPartRequestDecoder.

You may be affected by this vulnerability your project contains the following code patterns:

channelPipeline.addLast(new HttpPostRequestDecoder(...));

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-2021-21290 has been found in Oracle Netty.
Confidential information can be exposed externally. CVSS score: 6.2/10.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "Oracle Netty CVE-2021-21290" on the vendor's site.

CVE-2021-21290 (Oracle Netty) — CWE-378 / CVSS v3 6.2
Attack vector: local / unauthenticated / no user interaction
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-378) exists in Oracle Netty.

📍 Affected scope

Check the vendor advisory for the affected versions of Oracle Netty.

🔥 Severity

Severity: Medium (CVSS 6.2/10). Confidential information can be exposed externally.

🔧 How to fix

Update to the patched release per vendor advisory.

🛡️ 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

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

  1. 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。

  2. 2
    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-http
[{"type":"ECOSYSTEM","events":[{"introduced":"4.0.0"},{"fixed":"4.1.59.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

References

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