CVE-2026-42944
Publication date 20 May 2026
Last updated 22 May 2026
Ubuntu priority
Description
NLnet Labs Unbound 1.14.0 up to and including version 1.25.0 has a vulnerability that results in heap overflow when encoding multiple NSID and/or DNS Cookie EDNS and/or EDNS Padding options in the reply packet. The relevant options ('nsid', 'answer-cookie', 'pad-responses' (default)) need to be enabled for the vulnerability to be exploited. An adversary who can query Unbound can exploit the vulnerability by attaching multiple NSID and/or DNS Cookie EDNS and/or EDNS Padding options to the query. A flaw in the size calculation of the EDNS field truncates the correct value which allows the encoder to overflow the available space when writing. Those two combined lead to a heap overflow write of Unbound controlled data and eventually a crash. Unbound 1.25.1 contains a patch with a fix to de-duplicate the EDNS options and a fix to prevent truncation of the EDNS field size calculation.
Status
| Package | Ubuntu Release | Status |
|---|---|---|
| unbound | 26.04 LTS resolute |
Fixed 1.24.2-1ubuntu2.1
|
| 25.10 questing |
Fixed 1.22.0-2ubuntu2.3
|
|
| 24.04 LTS noble |
Fixed 1.19.2-1ubuntu3.8
|
|
| 22.04 LTS jammy |
Not affected
|
|
| 20.04 LTS focal |
Not affected
|
|
| 18.04 LTS bionic |
Not affected
|
|
| 16.04 LTS xenial |
Needs evaluation
|
|
| 14.04 LTS trusty |
Not affected
|
Notes
References
Related Ubuntu Security Notices (USN)
- USN-8282-1
- Unbound vulnerabilities
- 20 May 2026