Netty <4.1.135 / <4.2.15 HAProxy PROXY v2 codec memory leak (PP2_TYPE_SSL)
CVE-2026-48059 Published on June 12, 2026
Netty HAProxy: Unbalanced Reference Count in Nested PP2_TYPE_SSL TLV Parsing Leads to Memory Exhaustion
Netty is a network application framework for development of protocol servers and clients. Prior to versions 4.1.135.Final and 4.2.15.Final, the HAProxy PROXY protocol v2 codec in netty leaks native or heap memory on every connection when a client sends a syntactically valid header containing nested `PP2_TYPE_SSL` TLVs (type-length-value records) at depth two or greater. The leak occurs on the successful parse path no exception is thrown, the message fires downstream, the decoder removes itself, and the application releases the `HAProxyMessage` normally. Yet the underlying cumulation buffer (a pooled, potentially direct `ByteBuf` allocated by the channel) remains permanently pinned. Versions 4.1.135.Final and 4.2.15.Final patch the issue.
Weakness Type
What is a Memory Leak Vulnerability?
The software does not sufficiently track and release allocated memory after it has been used, which slowly consumes remaining memory. This is often triggered by improper handling of malformed data or unexpectedly interrupted sessions. In some languages, developers are responsible for tracking memory allocation and releasing the memory. If there are no more pointers or references to the memory, then it can no longer be tracked and identified for release.
CVE-2026-48059 has been classified to as a Memory Leak vulnerability or weakness.
Products Associated with CVE-2026-48059
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Affected Versions
netty:- Version >= 4.2.0.Final, < 4.2.15.Final is affected.
- Version < 4.1.135.Final is affected.