CVE-2026-48059: Netty HAProxy: Unbalanced Reference Count in Nested PP2_TYPE_SSL TLV Parsing Leads to Memory Exhaustion
Impact 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 PP2TYPESSL 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.
Other sources
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 PP2TYPESSL 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.
— MITRE
Affected Software
Event History
Frequently Asked Questions
What is the severity of CVE-2026-48059?
CVE-2026-48059 is classified as having a high severity with a CVSS score of 8.7.
How do I fix CVE-2026-48059?
To address CVE-2026-48059, upgrade to the latest version of the Netty HAProxy codec, specifically version 4.1.135 or 4.2.15 or later.
What causes CVE-2026-48059?
CVE-2026-48059 is caused by an unbalanced reference count during the parsing of nested PP2_TYPE_SSL TLVs in the HAProxy PROXY protocol v2 codec.
What are the consequences of CVE-2026-48059?
The consequences of CVE-2026-48059 include potential memory exhaustion leading to Denial of Service if exploited by attackers.
What software is affected by CVE-2026-48059?
CVE-2026-48059 affects the maven/io.netty:netty-codec-haproxy software.