CVE-2026-48059: Netty HAProxy Unbalanced Reference Count Vulnerability

HIGH
Advisory Identifier: GHSA-h2qv-fj59-j46j
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CVSS 7.5
CWE-1286 CWE-401
Published
Advisory Summary

CVE-2026-48059 is a HIGH (CVSS 7.5) unbalanced reference count vulnerability (CWE-1286: Improper Validation of Syntactic Correctness of Input) affecting Netty HAProxy libraries in the Maven ecosystem. The issue involves unbalanced reference count in nested pp2_type_ssl tlv parsing leads to memory exhaustion. Remediation is available by upgrading affected packages to version 4.2.15.Final, 4.1.135.Final.

CVE-2026-48059 at a Glance

CVE Identifier CVE-2026-48059
GHSA Identifier GHSA-h2qv-fj59-j46j
Severity HIGH
CVSS v3.1 Base Score 7.5
CWE Classification CWE-1286: Improper Validation of Syntactic Correctness of Input
Affected Product Netty HAProxy
Package Ecosystem Maven
Published Date
Last Updated

Security Impact

CVSS: 7.5

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality None (C:N)
Integrity None (I:N)
Availability High (A:H)

How to Fix CVE-2026-48059

To remediate this vulnerability, upgrade all affected Netty HAProxy dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

io.netty:netty-codec-haproxy fixed: 4.2.15.Final 
<dependency>
    <groupId>io.netty</groupId>
    <artifactId>netty-codec-haproxy</artifactId>
    <version>4.2.15.Final</version>
</dependency>
io.netty:netty-codec-haproxy fixed: 4.1.135.Final 
<dependency>
    <groupId>io.netty</groupId>
    <artifactId>netty-codec-haproxy</artifactId>
    <version>4.1.135.Final</version>
</dependency>
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

mvn dependency:tree -Dincludes=io.netty

How to Check if You Are Affected

To determine whether your Java application is affected by CVE-2026-48059, inspect your build dependencies using the Maven Dependency Plugin:

mvn dependency:tree -Dincludes=io.netty

Analyze the terminal output to locate any version of Netty HAProxy in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 4.2.15.Final), your application is affected.

Note: The mvn dependency:tree -Dincludes=io.netty command inspects the resolved dependency graph declared in your project's POM files; it does not perform automated security scanning or inspect runtime dynamic classpaths. Always verify runtime container classpaths and shaded JARs.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-1286: Improper Validation of Syntactic Correctness of Input, where the product receives input that is expected to be well-formed - i.e., to comply with a certain syntax - but it does not validate or incorrectly validates that the input complies with the syntax. In Netty HAProxy, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### 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 `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.

CVE-2026-48059 Affected Netty HAProxy Versions

2 component(s)
Fixed Versions:
4.2.15.Final4.1.135.Final
Product / Package Ecosystem Affected Versions Fixed Version
io.netty:netty-codec-haproxy
maven/io.netty/netty-codec-haproxy
Maven
≥ 4.2.0.Final
< 4.2.15.Final
4.2.15.Final
io.netty:netty-codec-haproxy
maven/io.netty/netty-codec-haproxy
Maven
< 4.1.135.Final
4.1.135.Final

References

GitHub Advisory / Wiki ADVISORY
https://github.com/netty/netty/security/advisories/GHSA-h2qv-fj59-j46j
NVD — CVE-2026-48059 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-48059
Netty HAProxy Security Information SECURITY
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-48059.json
Netty HAProxy Release RELEASE
https://github.com/netty/netty/releases/tag/netty-4.2.15.Final
Netty HAProxy Release RELEASE
https://github.com/netty/netty/releases/tag/netty-4.1.135.Final
Netty HAProxy Source Repository REPOSITORY
https://github.com/netty/netty
bugzilla.redhat.com/show_bug.cgi WEB
https://bugzilla.redhat.com/show_bug.cgi?id=2488437
Netty HAProxy Security Information SECURITY
https://access.redhat.com/security/cve/CVE-2026-48059
access.redhat.com/errata/rhsa-2026:66... WEB
https://access.redhat.com/errata/RHSA-2026:66488
access.redhat.com/errata/rhsa-2026:65... WEB
https://access.redhat.com/errata/RHSA-2026:65126
access.redhat.com/errata/rhsa-2026:54... WEB
https://access.redhat.com/errata/RHSA-2026:54435
access.redhat.com/errata/rhsa-2026:53... WEB
https://access.redhat.com/errata/RHSA-2026:53806
access.redhat.com/errata/rhsa-2026:53... WEB
https://access.redhat.com/errata/RHSA-2026:53646
access.redhat.com/errata/rhsa-2026:53... WEB
https://access.redhat.com/errata/RHSA-2026:53645
access.redhat.com/errata/rhsa-2026:53... WEB
https://access.redhat.com/errata/RHSA-2026:53644
access.redhat.com/errata/rhsa-2026:50... WEB
https://access.redhat.com/errata/RHSA-2026:50085
access.redhat.com/errata/rhsa-2026:48... WEB
https://access.redhat.com/errata/RHSA-2026:48151
access.redhat.com/errata/rhsa-2026:41... WEB
https://access.redhat.com/errata/RHSA-2026:41951
access.redhat.com/errata/rhsa-2026:37... WEB
https://access.redhat.com/errata/RHSA-2026:37390
access.redhat.com/errata/rhsa-2026:36... WEB
https://access.redhat.com/errata/RHSA-2026:36820
access.redhat.com/errata/rhsa-2026:34... WEB
https://access.redhat.com/errata/RHSA-2026:34608
access.redhat.com/errata/rhsa-2026:26... WEB
https://access.redhat.com/errata/RHSA-2026:26586
access.redhat.com/errata/rhsa-2026:26... WEB
https://access.redhat.com/errata/RHSA-2026:26018
access.redhat.com/errata/rhsa-2026:26... WEB
https://access.redhat.com/errata/RHSA-2026:26017

Frequently Asked Questions

What is CVE-2026-48059?
CVE-2026-48059 is a security vulnerability in Netty HAProxy involving Unbalanced Reference Count in Nested PP2_TYPE_SSL TLV Parsing Leads to Memory Exhaustion under CWE-1286: Improper Validation of Syntactic Correctness of Input.
Which Netty HAProxy versions are affected?
Affected versions include releases prior to 4.2.15.Final, 4.1.135.Final across affected packages: io.netty:netty-codec-haproxy.
What version fixes CVE-2026-48059?
Upgrading to 4.2.15.Final, 4.1.135.Final (or the latest patched release for your respective branch) resolves the vulnerability.
Is netty-codec-haproxy affected?
Yes, io.netty:netty-codec-haproxy is affected in releases prior to 4.2.15.Final, 4.1.135.Final. Upgrade your dependency to 4.2.15.Final, 4.1.135.Final or later.
What is the CVSS score of CVE-2026-48059?
CVE-2026-48059 has a CVSS v3.1 base score of 7.5 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
What CWE is associated with CVE-2026-48059?
CVE-2026-48059 is classified under CWE-1286: Improper Validation of Syntactic Correctness of Input (The product receives input that is expected to be well-formed - i.e., to comply with a certain syntax - but it does not validate or incorrectly validates that the input complies with the syntax.).
How can I check Maven dependencies for CVE-2026-48059?
Run the dependency tree command: 'mvn dependency:tree -Dincludes=io.netty'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
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  "details" : "### Impact\nThe 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.",
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    "type" : "WEB",
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  "database_specific" : {
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}