Netty QpackDecoder OOB Heap Before 4.2.13.Final
CVE-2026-42582 Published on May 13, 2026
Netty: HTTP/3 QPACK literal unbounded allocation
Netty is an asynchronous, event-driven network application framework. Prior to 4.2.13.Final, when decoding header blocks, the non-Huffman branch of io.netty.handler.codec.http3.QpackDecoder#decodeHuffmanEncodedLiteral may execute new byte[length] for a string literal before verifying that length bytes are actually present in the compressed field section. The wire encoding allows a very large length to be expressed in few bytes. There is no check that length <= in.readableBytes() before new byte[length]. This vulnerability is fixed in 4.2.13.Final.
Vulnerability Analysis
CVE-2026-42582 is exploitable 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
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.
What is a Stack Exhaustion Vulnerability?
The product allocates memory based on an untrusted, large size value, but it does not ensure that the size is within expected limits, allowing arbitrary amounts of memory to be allocated.
CVE-2026-42582 has been classified to as a Stack Exhaustion vulnerability or weakness.
Products Associated with CVE-2026-42582
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Affected Versions
netty:- Version >= 4.2.0.Alpha1, < 4.2.13.Final is affected.
- Version >= 4.2.0.Alpha1, < 4.2.13.Final is affected.