# CVE-2021-21290: libnetty-java: Netty is an open-source, asynchronous event-driven network applicationframework for rapid development of maintainable...

CVE-2021-21290 is fixed in 2 products on 1 platform, first by RLSA-2022:5498, released July 5, 2022. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2021-21290
- Priority: Routine
- CVSS: n/a (Medium)
- EPSS: 0.0180
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Feb 8, 2021

## Description

Netty is an open-source, asynchronous event-driven network applicationframework for rapid development of maintainable high performance protocolservers & clients. In Netty before version 4.1.59.Final there is avulnerability on Unix-like systems involving an insecure temp file. Whennetty's multipart decoders are used local information disclosure can occurvia the local system temporary directory if temporary storing uploads onthe disk is enabled. On unix-like systems, the temporary directory isshared between all user. As such, writing to this directory using APIs thatdo not explicitly set the file/directory permissions can lead toinformation disclosure. Of note, this does not impact modern MacOSOperating Systems. The method "File.createTempFile" on unix-like systemscreates a random file, but, by default will create this file with thepermissions "-rw-r--r--". Thus, if sensitive information is written to thisfile, other local users can read this information. This is the case innetty's "AbstractDiskHttpData" is vulnerable. This has been fixed inversion 4.1.59.Final. As a workaround, one may specify your own"java.io.tmpdir" when you start the JVM or use"DefaultHttpDataFactory.setBaseDir(...)" to set the directory to somethingthat is only readable by the current user.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | libdb rocky 8 | 0:5.3.28-42.el8_4 | [RLSA-2022:5498](https://patchblox.com/security/data/fix/linux/rlsa-2022-5498.md) | Jul 5, 2022 |
| Linux | libnetty-java Ubuntu 18.04.6 LTS (bionic) | 1:4.1.7-4ubuntu0.1+esm2 | [libnetty-java 1:4.1.7-4ubuntu0.1+esm2](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-libnetty-java-1-4.1.7-4ubuntu0.1-esm2.md) | Dec 12, 2022 |
| Linux | libnetty-java Ubuntu 20.04 LTS (focal) | 1:4.1.45-1ubuntu0.1~esm1 | [libnetty-java 1:4.1.45-1ubuntu0.1~esm1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-libnetty-java-1-4.1.45-1ubuntu0.1-esm1.md) | Dec 12, 2022 |
| Linux | libnetty-java Ubuntu 22.04.1 LTS (jammy) | 1:4.1.48-4+deb11u1build0.22.04.1 | [libnetty-java 1:4.1.48-4+deb11u1build0.22.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-libnetty-java-1-4.1.48-4-deb11u1build0.22.04.1.md) | Dec 12, 2022 |
| Linux | libnetty-java Ubuntu 24.10 (oracular) | 4.1.48-2 | [libnetty-java 4.1.48-2](https://patchblox.com/security/data/fix/linux/ubuntu-oracular-libnetty-java-4.1.48-2.md) | Jan 16, 2026 |
| Linux | libnetty-java Ubuntu 25.04 (plucky) | 4.1.48-2 | [libnetty-java 4.1.48-2](https://patchblox.com/security/data/fix/linux/ubuntu-plucky-libnetty-java-4.1.48-2.md) | Jan 16, 2026 |

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Data as of 2026-11-09T01:18:40Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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