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Advisory severityHigh7.5Red Hat Linux

High [CVE-2026-55851] Netty codec-haproxy: Denial of Service via crafted PROXY protocol v2 message

This high-severity Red Hat Linux advisory covers CVE-2026-55851 affecting Red Hat build of Apache Camel 4.18.3 for Spring Boot 3.5.16, Red Hat Build of Apache Camel 4.18 for Quarkus 3.33, Red Hat build of Quarkus 3.27.4.SP3.

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CVE-2026-55851 Source published Source updated

VulniPulse record published Record updated

CVE-2026-55851
Affected products & platforms
Red Hat LinuxUnclassified
Open source advisory

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Summary

Netty is a network application framework for development of protocol servers and clients.

In versions 4.2.0.Final up to (but not including) 4.2.16.Final, and 4.1.0.Final up to (but not including) 4.1.135, the `HAProxyMessageDecoder` in Netty's `codec-haproxy` module performs protocol version detection by reading the 13th byte as a signed Java `byte` and widening it to `int` without masking; a PROXY protocol v2 binary prefix followed by version byte `0xFF` sign-extends to `-1`, collides with the decoder's need-more-data sentinel, and causes `ByteToMessageDecoder` to accumulate inbound bytes in an unbounded `cumulation` buffer until direct memory is exhausted.

This issue is fixed in versions 4.1.136.Final and 4.2.16.Final. A remote attacker could exploit a vulnerability in the HAProxyMessageDecoder by sending a specially crafted PROXY protocol v2 message.

This leads to unbounded buffer accumulation, causing a denial of service (DoS) due to memory exhaustion. This impact is significant for applications that process PROXY protocol v2 messages using the affected Netty component.

Red Hat severity: Important — CVSS 7.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H). Weakness: CWE-770.

Affected versions
  • 4.2.0
  • 4.1.0
  • 4.1.135

Official advisory · high-confidence parse· fetched 12 days ago·verify at source

Fixed versions
  • 4.1.136
  • 4.2.16
  • netty-codec-haproxy
  • RHSA-2026:54622
  • RHSA-2026:48118
  • RHSA-2026:47189
  • RHSA-2026:47172

Official advisory · high-confidence parse· fetched 12 days ago·verify at source

Mitigation

Upgrade to a fixed release: 4.1.136, 4.2.16, netty-codec-haproxy, RHSA-2026:54622, RHSA-2026:48118, RHSA-2026:47189. That is the remediation for this advisory.

The vendor advisory may list additional interim mitigations or workarounds not captured here — review it before change work.

Official advisory · high-confidence parse· fetched 12 days ago·verify at source

Discussion(0)

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