Netty Lz4FrameDecoder DoS via Large 32MB Mem Allocation pre-4.2.13 & 4.1.133
CVE-2026-42583 Published on May 13, 2026
Netty: Lz4FrameDecoder resource exhaustion
Netty is an asynchronous, event-driven network application framework. Prior to 4.2.13.Final and 4.1.133.Final, Lz4FrameDecoder allocates a ByteBuf of size decompressedLength (up to 32 MB per block) before LZ4 runs. A peer only needs a 21-byte header plus compressedLength payload bytes - 22 bytes if compressedLength == 1 - to force that allocation. This vulnerability is fixed in 4.2.13.Final and 4.1.133.Final.
Vulnerability Analysis
CVE-2026-42583 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. An automatable proof of concept (POC) exploit exists. The potential impact of an exploit of this vulnerability is considered to have no impact on confidentiality and integrity, and a high impact on availability.
Weakness Types
What is a Resource Exhaustion Vulnerability?
The software does not properly control the allocation and maintenance of a limited resource, thereby enabling an actor to influence the amount of resources consumed, eventually leading to the exhaustion of available resources.
CVE-2026-42583 has been classified to as a Resource Exhaustion vulnerability or weakness.
Allocation of Resources Without Limits or Throttling
The software allocates a reusable resource or group of resources on behalf of an actor without imposing any restrictions on the size or number of resources that can be allocated, in violation of the intended security policy for that actor.
Products Associated with CVE-2026-42583
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Affected Versions
netty:- Version >= 4.2.0.Alpha1, < 4.2.13.Final is affected.
- Version < 4.1.133.Final is affected.
- Version < 4.1.133.Final is affected.
- Version < 4.2.13.Final is affected.