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Netty has an IPv6 Subnet Filter Bypass via Incorrect Comparator Masking

High severity GitHub Reviewed Published Jun 5, 2026 in netty/netty • Updated Jun 12, 2026

Package

maven io.netty:netty-handler (Maven)

Affected versions

>= 4.2.0.Final, <= 4.2.14.Final
<= 4.1.134.Final

Patched versions

4.2.15.Final
4.1.135.Final

Description

Summary

An attacker can bypass IPv6 subnet rules due to an incorrect masking operation in IpSubnetFilterRule.compareTo(). Valid public IP addresses can bypass the restrictions.

Details

io.netty.handler.ipfilter.IpSubnetFilterRule#compareTo(java.net.InetSocketAddress) method performs a bitwise AND between the incoming IP address and the configured networkAddress, instead of the subnetMask.

Impact

Access Control Bypass. Attacker can bypass IpSubnetFilter IPv6 access controls.

References

@chrisvest chrisvest published to netty/netty Jun 5, 2026
Published to the GitHub Advisory Database Jun 8, 2026
Reviewed Jun 8, 2026
Published by the National Vulnerability Database Jun 11, 2026
Last updated Jun 12, 2026

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
High
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(12th percentile)

Weaknesses

Improper Access Control

The product does not restrict or incorrectly restricts access to a resource from an unauthorized actor. Learn more on MITRE.

Incorrect Comparison

The product compares two entities in a security-relevant context, but the comparison is incorrect, which may lead to resultant weaknesses. Learn more on MITRE.

CVE ID

CVE-2026-44249

GHSA ID

GHSA-3qp7-7mw8-wx86

Source code

Credits

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