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CVE
CVE-2026-44249
Netty is a network application framework for development of protocol servers and clients. In netty-handler prior to vers
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.
HIGH · CVSS 8.1
EPSS 0.00039
Schedule remediation
- CVSS base score ≥ 7.0
Sigma rules0
YARA rules0
Look this up elsewhere - one-click external pivots
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How to read a CVE - triage first, then detect and patch
This page is every public fact about CVE-2026-44249, cross-linked. Its job is to answer one question fast - does this need my attention now? - and then hand you the two things you do about it. Here is how an analyst reads it.
Triage: should I act now? Four signals, and they are not interchangeable:
CVSSseverity - how bad it is IF exploited, 0-10. A high CVSS alone is not urgency; a flaw can be a perfect 10 and never actually be attacked.
EPSSprobability - a model’s estimate of the chance it is exploited in the next 30 days, 0-1. This is the “will it actually happen” signal.
CISA KEVconfirmed - it is being exploited in the wild right now. The strongest signal on the page; KEV beats any score.
Weaponisedavailability - public exploits / PoCs, and especially Metasploit modules rated Excellent / Great. Reliable, packaged exploit code means low-skill attackers can use it today.
How they combine: KEV, or a dependable Metasploit module, means patch now regardless of CVSS. High CVSS + low EPSS + no exploit is real but not an emergency - schedule it. Low CVSS but KEV-listed still gets patched now. The verdict above already weighed these for you; this is how it got there.
Then what - two workflows:
Detectwhen you cannot patch today, follow this CVE to the ATT&CK techniques it enables, then Build a SIEM detection (the green button) - author a rule, test it in Atomic, deploy it. That buys visibility while the patch waits.
PatchAffected products / packages tell you if you are exposed; Fixed versions by distribution and Vendor advisories give the exact version that closes it.
Reading order for the panels below: verdict + badges, then Public exploits / Metasploit (is it weaponised), then ATT&CK techniques + Sigma / IDS rules (can I detect it), then Affected products / packages + Fixed versions (am I exposed, what patches it), then Threat actors / IOCs (who uses it), then Scoring & timeline / references (the evidence).
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ATT&CK techniques
20Techniques this CVE enables - linked via CWECAPECATT&CK. High◆ = named directly in ATT&CK or Nuclei templates.
T1014 · Rootkit T1027 · Obfuscated Files or Information T1027.009 · Embedded Payloads T1037 · Boot or Logon Initialization Scripts T1080 · Taint Shared Content T1505.005 · Terminal Services DLL T1542.003 · Bootkit T1543 · Create or Modify System Process T1543.001 · Launch Agent T1543.003 · Windows Service T1543.004 · Launch Daemon T1546.001 · Change Default File Association T1546.004 · Unix Shell Configuration Modification T1546.008 · Accessibility Features T1546.016 · Installer Packages T1547 · Boot or Logon Autostart Execution T1547.006 · Kernel Modules and Extensions T1553.004 · Install Root Certificate T1556.006 · Multi-Factor Authentication T1562.001 · Disable or Modify Tools
▤ Build a SIEM detection for these techniques
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CAPEC attack patterns
12Attack patterns this CVE enables - the bridge from weakness to ATT&CK technique.
CAPEC-CAPEC-10 · Buffer Overflow via Environment Variables CAPEC-CAPEC-120 · Double Encoding CAPEC-CAPEC-14 · Client-side Injection-induced Buffer Overflow CAPEC-CAPEC-15 · Command Delimiters CAPEC-CAPEC-182 · Flash Injection CAPEC-CAPEC-19 · Embedding Scripts within Scripts CAPEC-CAPEC-24 · Filter Failure through Buffer Overflow CAPEC-CAPEC-267 · Leverage Alternate Encoding CAPEC-CAPEC-3 · Using Leading 'Ghost' Character Sequences to Bypass Input Filters CAPEC-CAPEC-41 · Using Meta-characters in E-mail Headers to Inject Malicious Payloads CAPEC-CAPEC-43 · Exploiting Multiple Input Interpretation Layers CAPEC-CAPEC-44 · Overflow Binary Resource File
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Weakness Classification
CWE-284Improper Access Control
CWE-697Incorrect Comparison
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Affected Packages
1Language-ecosystem packages (from OSV) tied to this CVE, with the version that fixes it - the dependency-level detail NVD doesn’t carry.
Maven
io.netty:netty-handler
HIGH
fixed in 4.2.15.Final
📦
Fixed versions by distribution
2The package version that resolves this CVE on each Linux distribution, from the vendor’s published security data. fixed in shows a patched version exists; open means the package is listed as affected with no fix yet.
suse sle15netty-tcnative open
suse sle15netty3 open
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Scoring & Timeline
8.1
HIGH · CVSS v3.1 · [email protected]
Attack Vector
Network
Adjacent
Local
Physical
Attack Complexity
Low
High
Privileges Required
None
Low
High
User Interaction
None
Required
Scope
Unchanged
Changed
Confidentiality
None
Low
High
Integrity
None
Low
High
Availability
None
Low
High
SSVC triage · cisa-vulnrichment
Exploitation
none
Automatable
no
Technical impact
total
SSVC asks the questions that actually drive patch urgency: is it being exploited, can attacks be automated, and how total is the impact.