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Fencer Vulns
high 7.5

CVE-2026-55851 json

Netty codec-haproxy: Signed-Byte Sentinel Collision in HAProxyMessageDecoder Leads to Unbounded Memory Exhaustion

published 2026-07-21 3 mo ago modified 2026-09-10 1 mo ago also EUVD-2026-46438 , GHSA-q6cq-mhr2-jmr5

cvss
7.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.6%
EPSS 0.6% chance of exploitation in 30 days, percentile 50%
public exploits
0
none known

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.

Patch / fix

  • maven io.netty:netty-codec-haproxy 4.1.136.Final, 4.2.16.Final
  • io.netty netty-codec-haproxy 4.1.136.Final, 4.2.16.Final
  • netty netty 4.1.136.Final, 4.2.16.Final
  • netty-tcnative SLES for SAP 15 SP6, SLES for SAP 15 SP5, SLES for SAP 15 SP4 +8 more 2.0.80-150200.3.48.1
  • netty SLE Module for Package Hub 15 SP7 4.1.136-150200.4.53.1

suse advisories SUSE-SU-2026:3482-1

  • netty openSUSE Tumbleweed 4.1.136-1.1

opensuse advisories openSUSE-SU-2026:11394-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-55851 updated cvss 7.5

io.netty/netty-codec-haproxy: Netty codec-haproxy: Denial of Service via crafted PROXY protocol v2 message

  • Red Hat OpenShift Serverless openshift-serverless-1/kn-ekb-receiver-rhel9, openshift-serverless-1/kn-ekb-dispatcher-rhel9, openshift-serverless-1/kn-eventing-integrations-log-sink-rhel9, openshift-serverless-1/kn-eventing-integrations-aws-s3-sink-rhel9, openshift-serverless-1/kn-eventing-integrations-aws-sns-sink-rhel9, openshift-serverless-1/kn-eventing-integrations-aws-sqs-sink-rhel9, +4 more Red Hat build of Apache Camel - HawtIO 4 netty-codec-haproxy 4.1.135.Final-redhat-00001 Red Hat build of Apache Camel 4 for Quarkus 3 netty-codec-haproxy 4.1.135.Final-redhat-00001 Red Hat build of Apicurio Registry 3 netty-codec-haproxy 4.1.135.Final-redhat-00001
    affected: no fix available
  • Red Hat build of Debezium 3 netty-codec-haproxy 4.1.135.Final-redhat-00001
    affected: no fix planned “Will not fix”
  • Red Hat Build of Keycloak rhbk-keycloak-rhel9, rhbk-rhel9-operator, rhbk-openshift-rhel9, rhbk-keycloak-rhel9-operator, netty-codec-haproxy 4.1.135.Final-redhat-00001
    affected: no fix available
  • Red Hat build of Quarkus netty-codec-haproxy 4.1.135.Final-redhat-00001 Red Hat JBoss Enterprise Application Platform 7 eap74-els-openjdk8-openshift-rhel8, eap74-els-openjdk11-openshift-rhel8, eap74-els-openjdk17-openshift-rhel8, jboss-eap-7-eap74-els-openjdk8-openshift-rhel8, netty-codec-haproxy 4.1.135.Final-redhat-00001, jboss-eap-7-eap74-els-openjdk17-openshift-rhel8 Red Hat Single Sign-On 7 netty-codec-haproxy 4.1.135.Final-redhat-00001
    affected: no fix available “Fix deferred”
  • Red Hat streams for Apache Kafka 3 netty-codec-haproxy 4.1.135.Final-redhat-00001
    affected: no fix available
  • Red Hat Cryostat 4 on RHEL 9 cryostat/cryostat-rhel9 4.2.0-14, cryostat/jfr-datasource-rhel9 4.2.0-14, cryostat/cryostat-reports-rhel9 4.2.0-14
    fixed: vendor fix RHSA-2026:68333
  • Red Hat AMQ Broker 7.14.1
    fixed: vendor fix RHSA-2026:66488
  • Red Hat Build of Apache Camel 3.33.2.SP3 netty-codec-haproxy 4.1.136.Final-redhat-00001
    fixed: vendor fix RHSA-2026:48118
show 14 more
  • Red Hat build of Apache Camel 4.18.3 for Spring Boot 3.5.16
    fixed: vendor fix RHSA-2026:54622
  • Red Hat build of Keycloak 26.4.14
    fixed: vendor fix RHSA-2026:50846
  • Red Hat build of Keycloak 26.6.5
    fixed: vendor fix RHSA-2026:50848
  • Red Hat build of Quarkus 3.27.4.SP3 netty-codec-haproxy 4.1.136.Final-redhat-00001
    fixed: vendor fix RHSA-2026:47189
  • Red Hat build of Quarkus 3.33.2.SP3 netty-codec-haproxy 4.1.136.Final-redhat-00001
    fixed: vendor fix RHSA-2026:47172
  • Red Hat Data Grid 8.6.3
    fixed: vendor fix RHSA-2026:69296
  • Red Hat OpenShift AI 2.25 rhoai/odh-trustyai-service-rhel9 1788198681
    fixed: vendor fix RHSA-2026:65126
  • Red Hat OpenShift AI 3.4 rhoai/odh-trustyai-service-rhel9 1791792525
    fixed: vendor fix RHSA-2026:84734
  • Red Hat OpenShift Dev Spaces 3.31 devspaces/multicluster-redirector-rhel9 1792491532
    fixed: vendor fix RHSA-2026:90321
  • Red Hat Cryostat 4 on RHEL 9 cryostat/cryostat-db-rhel9 4.2.0-22, cryostat/cryostat-storage-rhel9 4.2.0-22, cryostat/cryostat-rhel9-operator 4.2.0-21, cryostat/cryostat-operator-bundle 4.2.0-12, cryostat/cryostat-agent-init-rhel9 0.7.0-12, cryostat/cryostat-grafana-dashboard-rhel9 4.2.0-14, +1 more Red Hat Build of Apache Camel 3.33.2.SP3 jimfs 1.1, jna 5.8.0, bcel 6.7.0, bson 5.6.4, gax 2.74.1, icu4j 78.2, +1630 more Red Hat build of Quarkus 3.27.4.SP3 jna 5.8.0, db2 1.21.4, h2 2.3.230, y18n 5.0.8, cliui 8.0.1, guice 5.1.0, +1009 more Red Hat build of Quarkus 3.33.2.SP3 jna 5.8.0, bson 5.6.4, h2 2.4.240, y18n 5.0.8, cliui 8.0.1, guice 5.1.0, +1018 more
    not affected: vulnerable code not present
  • Red Hat JBoss Enterprise Application Platform Expansion Pack netty-codec-haproxy 4.1.135.Final-redhat-00001
    not affected: component not present
  • Red Hat OpenShift AI 2.25 rhoai/odh-rhel9-operator 1788331391, rhoai/odh-vllm-cpu-rhel9 1786712073, rhoai/odh-dashboard-rhel9 1788312226, rhoai/odh-modelmesh-rhel9 1788319539, rhoai/odh-operator-bundle 1788332816, rhoai/odh-vllm-cuda-rhel9 1786710989, +70 more Red Hat OpenShift AI 3.4 rhoai/odh-cli-rhel9 1791509689, rhoai/rhai-cli-rhel9 1791509689, rhoai/odh-automl-rhel9 1791535789, rhoai/odh-mlflow-rhel9 1791865967, rhoai/odh-autorag-rhel9 1791557539, rhoai/odh-trainer-rhel9 1791869783, +99 more Red Hat OpenShift Dev Spaces 3.31 devspaces/udi-rhel9 1792708612, devspaces/code-rhel9 1792599388, devspaces/server-rhel9 1792775639, devspaces/openvsx-rhel9 1792494821, devspaces/traefik-rhel9 1792464177, devspaces/udi-base-rhel9 1792686842, +9 more
    not affected: vulnerable code not present
  • Red Hat Satellite 6 candlepin, candlepin-selinux
    not affected: vulnerable code not in execute path
  • Red Hat streams for Apache Kafka 2 netty-codec-haproxy 4.1.135.Final-redhat-00001
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
partial
Assessed
3 mo ago

Exploit prediction

0.63% chance of exploitation in the next 30 days, higher than 50% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 4.0 8.7 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
CNA 4.0 8.7 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
NVD 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected packages

ecosystem package affected fixed in
maven io.netty:netty-codec-haproxy
>=4.2.0.Final, <4.2.16.Final
>=4.1.0.Final, <4.1.136.Final
4.2.16.Final
4.1.136.Final

Affected products

  • netty netty

Classification

Weakness
  • CWE-400 Uncontrolled Resource Consumption

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.