CVE-2026-44249Network attack vector

IPv6 access-control bypass via incorrect subnet masking

Published Jun 11, 2026 · Updated Jun 11, 2026

Access-control bypass in Netty netty-handler before 4.1.135.Final and 4.2.0.Final through 4.2.14.Final lets remote attackers evade IPv6 subnet rules. IpSubnetFilterRule.compareTo() applies bitwise AND to the incoming address and configured network address instead of the subnet mask. Exploitation requires an application to use IpSubnetFilter for IPv6 filtering, after which a valid public IPv6 address can pass a rule that should reject it.

CVSS severity8.1
High
EPSS probability1.03%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Access-control bypass in Netty netty-handler before 4.1.135.Final and 4.2.0.Final through 4.2.14.Final lets remote attackers evade IPv6 subnet rules. IpSubnetFilterRule.compareTo() applies bitwise AND to the incoming address and configured network address instead of the subnet mask. Exploitation requires an application to use IpSubnetFilter for IPv6 filtering, after which a valid public IPv6 address can pass a rule that should reject it.

The record

CVE
CVE-2026-44249
Published
Jun 11, 2026
Updated
Jun 11, 2026
Vendor
The Netty Project
Product
Netty
Classifications
CWE-284, CWE-697, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 11, 2026CVE publishedPublication date reported by the CVE source.
  2. Jun 11, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 4.1.135.Final
  2. Affected versionversion=>= 4.2.0.Final, < 4.2.15.Final

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Netty Project · Nettyversion=< 4.1.135.Final; version=>= 4.2.0.Final, < 4.2.15.Final

Published CVSS scores

8.1GitHubCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-284Improper Access Control
CWE-697Incorrect Comparison
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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