Netty Bzip2Decoder DoS via RLE state machine, fixed in v4.1.136/4.2.16
CVE-2026-59901 Published on July 29, 2026
Netty Bzip2Decoder: Infinite Loop in RLE State Machine Leads to Event-Loop Thread Hang
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.
Vulnerability Analysis
CVE-2026-59901 can be exploited with network access, and does not require authorization privileges or user interaction. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have no impact on confidentiality and integrity and availability.
Weakness Type
What is an Infinite Loop Vulnerability?
The program contains an iteration or loop with an exit condition that cannot be reached, i.e., an infinite loop. If the loop can be influenced by an attacker, this weakness could allow attackers to consume excessive resources such as CPU or memory.
CVE-2026-59901 has been classified to as an Infinite Loop vulnerability or weakness.
Products Associated with CVE-2026-59901
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Affected Versions
netty:- Version >=4.2.0.Final, < 4.2.16.Final is affected.
- Version < 4.1.136.Final is affected.