Netty: [Bzip2Decoder] Infinite Loop in RLE State Machine Leads to Event-Loop Thread Hang

HIGH 7.5CVE-2026-59901 · GHSA-558v-64gr-wgg4 · Published 29/07/2026 · updated 06/08/2026

Package	Affected versions	Patched versions
io.netty:netty-codec Maven	`< 4.1.136.Final`	`4.1.136.Final`
io.netty:netty-codec-compression Maven	`≥ 4.2.0.Final, < 4.2.16.Final`	`4.2.16.Final`
netty netty	`≥ 4.2.0, < 4.2.16< 4.1.136`	`4.2.164.1.136`

Description

The Bzip2Decoder handler in Netty's compression codec pipeline is vulnerable to a denial-of-service attack through a malformed bzip2 stream that permanently captures the event-loop thread in an infinite loop. The vulnerability exists in the run-length encoding (RLE) state machine within [Bzip2BlockDecompressor.read()]

NVD description

Netty is an asynchronous, event-driven network application framework. Prior to versions 4.1.136.Final and 4.2.16.Final, the `Bzip2Decoder` handler in Netty's compression codec pipeline is vulnerable to a denial-of-service attack through a malformed bzip2 stream that permanently captures the event-loop thread in an infinite loop. The vulnerability exists in the run-length encoding (RLE) state machine within [`Bzip2BlockDecompressor.read()`]. This issue has been fixed in versions 4.1.136.Final and 4.2.16.Final.

References

netty/netty security advisory · WEB
netty/netty · PACKAGE
netty/netty release netty-4.1.136.Final · WEB
netty/netty release netty-4.2.16.Final · WEB

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