io.netty/netty-codec-http2: Netty: Improper header neutralization in netty-codec-http2 (CVE-2026-59900)

Overview

A flaw was found in Netty's netty-codec-http2 component. The HTTP/2 encoder does not properly handle special characters in HTTP headers. This vulnerability allows a remote attacker to craft specific HTTP/2 requests, leading to HTTP response splitting and header injection attacks. Such attacks can enable an attacker to manipulate web content or inject malicious headers.

Vendor advisories

• RHSA-2026:47189 · Red Hat · fixed in: Red Hat build of Quarkus 3.27.4.SP3 · released 2026-07-29 · advisory
• RHSA-2026:47172 · Red Hat · fixed in: Red Hat build of Quarkus 3.33.2.SP3 · released 2026-07-30 · advisory
• Red Hat VEX · Moderate · affected: Cryostat 4, OpenShift Serverless, Red Hat AMQ Broker 7, Red Hat build of Apache Camel - HawtIO 4, Red Hat build of Apache Camel 4 for Quarkus 3, Red Hat build of Apache Camel for Spring Boot 4, … · no fix planned: Red Hat Build of Keycloak, Red Hat build of Quarkus, Red Hat Data Grid 8, Red Hat JBoss Enterprise Application Platform 7, … · updated 2026-10-20 · vex

io.netty/netty-codec-http2: Netty: Improper header neutralization in netty-codec-http2 — rated Moderate by Red Hat. Released 2026-07-09, updated 2026-10-20.

Affected:

• Cryostat 4
• OpenShift Serverless
• Red Hat AMQ Broker 7
• Red Hat build of Apache Camel - HawtIO 4
• Red Hat build of Apache Camel 4 for Quarkus 3
• Red Hat build of Apache Camel for Spring Boot 4
• Red Hat build of Apicurio Registry 3
• Red Hat build of Debezium 3
• Red Hat Build of Keycloak
• Red Hat build of Quarkus
• Red Hat Data Grid 8
• Red Hat Enterprise Linux AI (RHEL AI) 3
• Red Hat JBoss Enterprise Application Platform 7
• Red Hat JBoss Enterprise Application Platform Expansion Pack
• Red Hat OpenShift AI (RHOAI)
• Red Hat OpenShift Dev Spaces
• Red Hat Single Sign-On 7
• streams for Apache Kafka 2
• streams for Apache Kafka 3

Fixed:

• Red Hat build of Quarkus 3.27.4.SP3
• Red Hat build of Quarkus 3.33.2.SP3

No fix planned:

• Red Hat Build of Keycloak
• Red Hat build of Quarkus
• Red Hat Data Grid 8
• Red Hat JBoss Enterprise Application Platform 7
• Red Hat Single Sign-On 7
• streams for Apache Kafka 2
• Cryostat 4
• OpenShift Serverless
• Red Hat AMQ Broker 7
• Red Hat build of Apache Camel - HawtIO 4
• Red Hat build of Apache Camel 4 for Quarkus 3
• Red Hat build of Apache Camel for Spring Boot 4
• Red Hat build of Apicurio Registry 3
• Red Hat build of Debezium 3
• Red Hat Enterprise Linux AI (RHEL AI) 3
• Red Hat JBoss Enterprise Application Platform Expansion Pack
• Red Hat OpenShift AI (RHOAI)
• Red Hat OpenShift Dev Spaces
• streams for Apache Kafka 3

Not affected:

• Red Hat build of Quarkus 3.27.4.SP3
• Red Hat build of Quarkus 3.33.2.SP3

Remediation

Before applying this update, make sure all previously released errata relevant to your system have been applied.

For details on how to apply this update, refer to:

https://access.redhat.com/articles/11258 https://access.redhat.com/errata/RHSA-2026:47189 Before applying this update, make sure all previously released errata relevant to your system have been applied.

For details on how to apply this update, refer to:

https://access.redhat.com/articles/11258 https://access.redhat.com/errata/RHSA-2026:47172

Workarounds / mitigations:

• • Upgrade netty-codec-http2 to version 4.1.136.Final (4.1.x branch) or 4.2.16.Final (4.2.x branch).
• If upgrading is not immediately possible, ensure that HTTP/2 traffic is routed through a reverse proxy or WAF that validates and sanitizes HTTP headers before forwarding to the Netty-based application.

Package advisory (CVE-2026-59900)

Affected packages:

• io.netty:netty-codec-http2 >= 4.2.0.Final, <= 4.2.15.Final
• io.netty:netty-codec-http2 < 4.1.136.Final

Patched in:

• io.netty:netty-codec-http2 4.2.16.Final
• io.netty:netty-codec-http2 4.1.136.Final

Source: https://github.com/advisories/GHSA-c69g-56f8-xwqj