CVE-2026-48059 — Netty HAProxy: Unbalanced Reference Count in Nested PP2_TYPE_SSL TLV Parsing Leads to Memory Exhaustion

Description (CNA)

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.

Affected (CNA)

Vendor / product	Versions
netty / netty	affected >= 4.2.0.Final, < 4.2.15.Final; affected < 4.1.135.Final

CWE

CWE-401

References

ADP enrichment

CISA-ADP

No English description supplied.

No references supplied.

redhat-SADP

A flaw was found in the Netty HAProxy PROXY protocol v2 codec. A remote attacker can exploit this vulnerability by sending a specially crafted HAProxy PROXY protocol v2 header with nested `PP2_TYPE_SSL` type-length-value (TLV) records. This can lead to a memory leak, causing the underlying cumulation buffer to remain permanently pinned and potentially resulting in a Denial of Service (DoS) due to resource exhaustion.