Reference page — cumulative record through Monday, October 19, 2026 UTC. Reference pages update as the archive grows; only dated daily editions are immutable pages of record.
netty netty — Local Information Disclosure Vulnerability in Netty on Unix-Like systems due temporary files
AV AC PR UI S C I A CVSS EPSS %ile KEV
L L L N U H N N 5.5 .0178 77.9 —
AFFECTED
Product Versions Fixed
netty < 4.1.59.Final – —
TIMELINE
Dec 22 Reserved by GitHub_M
Feb 8 Published (CNA: GitHub_M)
Oct 8 EXPLOIT PUBLISHED — CVE-2021-21290 (netty). Public exploit reference added.
Oct 8 RESCORED — CVE-2021-21290 (netty). CVSS 6.2 → 5.5 (NVD).
Description
Netty is an open-source, asynchronous event-driven network application framework for rapid development of maintainable high performance protocol servers & clients. In Netty before version 4.1.59.Final there is a vulnerability on Unix-like systems involving an insecure temp file. 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. 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. This has been fixed in version 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 something that is only readable by the current user.
About this page
This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2021-21290 from the CVE Program record, NVD enrichment, the CISA KEV catalog, EPSS, and OSV advisories. The box score's numbers (CVSS, EPSS, KEV status) are current as of Monday, October 19, 2026 UTC and are re-derived as the archive grows; only dated daily editions are immutable pages of record. The authoritative source for this identifier is cve.org.
