CVE-2026-42944 Affecting unbound package, versions <1.22.0-2+deb13u3


Severity

Recommended
0.0
high
0
10

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Threat Intelligence

EPSS
0.84% (54th percentile)

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  • Snyk IDSNYK-ECHOLATEST-UNBOUND-18234974
  • published23 Jul 2026
  • disclosed20 May 2026

Introduced: 20 May 2026

CVE-2026-42944  (opens in a new tab)

How to fix?

Upgrade Echo:latest unbound to version 1.22.0-2+deb13u3 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream unbound package and not the unbound package as distributed by Echo. See How to fix? for Echo:latest relevant fixed versions and status.

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.

CVSS Base Scores

version 3.1