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High, CVSS 8.1

Netty has an IPv6 Subnet Filter Bypass via Incorrect Comparator Masking

CVE-2026-44249GHSA-3qp7-7mw8-wx86

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (io.netty:netty-handler 4.2.15.Final, 4.1.135.Final), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

  • Maven io.netty:netty-handler

    Affected
    >= 4.2.0.Final, <= 4.2.14.Final<= 4.1.134.Final
    Fixed in
    4.2.15.Final, 4.1.135.Final

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
8.1 · CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS
  • CVE-2026-44249: 0.99% estimated exploitation activity in the next 30 days; percentile 62.47 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

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.

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 1 · created ·

    Published from ghsa record GHSA-3qp7-7mw8-wx86

Agent brief

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# Patch Next advisory brief: CVE-2026-44249

Advisory: Netty has an IPv6 Subnet Filter Bypass via Incorrect Comparator Masking
IDs: CVE-2026-44249, GHSA-3qp7-7mw8-wx86
Record: https://patchnext.com/advisories/cve-2026-44249 (revision 1, source checked 26 Oct 2026, 16:46 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: io.netty:netty-handler 4.2.15.Final, 4.1.135.Final. A vendor fix does not mean a deployment is fixed.

## Affected components
- Maven io.netty:netty-handler: affected >= 4.2.0.Final, <= 4.2.14.Final; <= 4.1.134.Final; fixed in 4.2.15.Final, 4.1.135.Final

## Suggested inspection (read-only)
- Maven io.netty:netty-handler: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on io.netty:netty-handler.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-3qp7-7mw8-wx86 (GitHub-reviewed advisory GHSA-3qp7-7mw8-wx86 lists affected ranges: Maven io.netty:netty-handler >=4.2.0.Final =0 <=4.1.134.Final)

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