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

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.

Published: 2026-06-11 Last update: 2026-06-17 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2026-44249 is rated Moderate Risk (43.6/100): CVSS High severity, with low exploitation likelihood (EPSS 0.41%). Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2026-44249

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-23 0.51% 0.41% -0.11%
2 2026-06-15 0.04% 0.51% +0.47%
3 2026-06-12 — 0.04% —

Full EPSS history (3 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-44249

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
8.1 3.1 HIGH
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:H)
Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 2.2 5.9 [email protected]

Weakness enumeration for CVE-2026-44249

GitHub Security Advisory for CVE-2026-44249

GHSA-3qp7-7mw8-wx86 · Severity: high · Ecosystem: maven — Netty has an IPv6 Subnet Filter Bypass via Incorrect Comparator Masking

OS Trackers for CVE-2026-44249

vendor priority summary link
debian not yet assigned CVE-2026-44249 not yet assigned priority: Debian including 1 source packages (netty), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): open 5. https://security-tracker.debian.org/tracker/CVE-2026-44249
redhat high — https://access.redhat.com/security/cve/CVE-2026-44249
suse high CVE-2026-44249 severity important: SUSE including 2 source package names (netty-tcnative, netty3), 24 product×package rows across 12 product lines (SUSE Linux Enterprise High Performance Computing 15 SP4-LTSS, SUSE Linux Enterprise High Performance Computing 15 SP5-LTSS, … (12 product lines)): Known Not Affected 24. https://www.suse.com/security/cve/CVE-2026-44249/
ubuntu medium CVE-2026-44249 medium priority: Ubuntu including 1 source packages (netty), 8 status rows across 8 suites (bionic, focal, jammy, noble, questing, resolute, trusty, upstream): needs-triage 8. https://ubuntu.com/security/CVE-2026-44249

Affected software / configurations for CVE-2026-44249

Vendor Product Version Raw CPE
netty netty < 4.1.135 cpe:2.3:a:netty:netty:*:*:*:*:*:*:*:*
netty netty >= 4.2.0, < 4.2.15 cpe:2.3:a:netty:netty:*:*:*:*:*:*:*:*

References for CVE-2026-44249

cvelogic Threat Intelligence