Prior to 4.2.13.Final and 4.1.133.Final, Netty's DNS codec does not enforce RFC 1035 domain name constraints during either encoding or decoding. (CVE-2026-42579)
Description
Netty versions prior to 4.2.13.Final and 4.1.133.Final have a vulnerability in their DNS codec where RFC 1035 domain name constraints are not enforced during encoding or decoding. This flaw allows malicious DNS responses or user-influenced hostnames to exploit the codec. The issue is fixed in versions 4.2.13.Final and 4.1.133.Final.
CVSS v3.1
Score 9.1critical
Affected software
pkg:deb/ubuntu/netty?arch=source&distro=esm-apps/focalpkg:deb/ubuntu/netty?arch=source&distro=esm-apps/jammypkg:deb/ubuntu/netty?arch=source&distro=esm-apps/noblepkg:deb/ubuntu/netty?arch=source&distro=questingpkg:deb/ubuntu/netty?arch=source&distro=stonkingpkg:deb/ubuntu/netty?arch=source&distro=esm-apps/resoluteRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
Netty, an asynchronous event-driven network application framework, contains a vulnerability (CVE-2026-42579) in its DNS codec in versions before 4.2.13.Final and 4.1.133.Final. The DNS codec does not enforce RFC 1035 domain name constraints during encoding or decoding, creating a bidirectional attack surface. Malicious DNS responses can exploit the decoder, and user-influenced hostnames can exploit the encoder. This vulnerability has a CVSS 3.1 score of 9.1, indicating high severity, and is fixed in the specified versions.
Potential Impact
The vulnerability allows attackers to exploit the DNS codec by sending malicious DNS responses or crafting hostnames that bypass domain name constraints. This can lead to integrity and availability impacts as indicated by the CVSS vector (C:N/I:H/A:H). There is no indication of confidentiality impact. No known exploits are reported in the wild at this time.
Mitigation Recommendations
A fix is available and has been released in Netty versions 4.2.13.Final and 4.1.133.Final. Users should upgrade to these or later versions to remediate the vulnerability. Refer to the official Ubuntu security notice USN-8401-1 for patch details and application instructions.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- UBUNTU-CVE-2026-42579
- Osv Schema Version
- 1.7.0
- Ecosystems
- ["Ubuntu:Pro:20.04:LTS","Ubuntu:Pro:22.04:LTS","Ubuntu:Pro:24.04:LTS","Ubuntu:25.10","Ubuntu:26.10","Ubuntu:Pro:26.04:LTS"]
- Cvss Version
- 3.1
Patch Information
Threat ID: 6ad3f6812cdf04f6566671e4
Added to database: 10/17/2026, 22:28:17 UTC
Last enriched: 10/18/2026, 01:41:04 UTC
Last updated: 10/18/2026, 01:41:04 UTC
Views: 8
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