What’s Vulnerable › Vulnerabilities

CVE-2026-44249: Netty has an IPv6 Subnet Filter Bypass via Incorrect Comparator Masking

• Severity: high (CVSS 8.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.0% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-06-11 · updated 2026-09-18
• Weakness: CWE-284

Description

Netty is a network application framework for development of protocol servers and clients. In netty-handler prior to versions 4.1.135.Final and 4.2.15.Final, an attacker can bypass IPv6 subnet rules due to an incorrect masking operation in IpSubnetFilterRule.compareTo(). Valid public IP addresses can bypass the restrictions. Versions 4.1.135.Final and 4.2.15.Final patch the issue.

Affected products

• netty: before 4.1.135; from 4.2.0 before 4.2.15 — fixed in 4.1.135, 4.2.15

How to fix

Upgrade to a fixed version: netty 4.1.135, 4.2.15. Check the vendor advisory for mitigations.

References

• https://github.com/netty/netty/releases/tag/netty-4.1.135.Final
• https://github.com/netty/netty/releases/tag/netty-4.2.15.Final
• https://github.com/netty/netty/security/advisories/GHSA-3qp7-7mw8-wx86
• https://access.redhat.com/errata/RHSA-2026:26017
• https://access.redhat.com/errata/RHSA-2026:26018
• https://access.redhat.com/errata/RHSA-2026:26586
• https://access.redhat.com/errata/RHSA-2026:28573
• https://access.redhat.com/errata/RHSA-2026:34608
• https://access.redhat.com/errata/RHSA-2026:36820
• https://access.redhat.com/errata/RHSA-2026:37390
• https://access.redhat.com/errata/RHSA-2026:41951
• https://access.redhat.com/errata/RHSA-2026:48124

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