CVE-2026-42944 (High) detected in multiple libraries

[mend-bolt-for-github]

CVE-2026-42944 - High Severity Vulnerability

Vulnerable Libraries - src4.0.4, src4.0.4, src4.0.4

src4.0.4

Library home page: https://github.com/MidnightBSD/src.git

Vulnerable Source Files (3)

/contrib/unbound/util/data/msgencode.c
/contrib/unbound/util/data/msgparse.c
/contrib/unbound/util/data/msgencode.h

src4.0.4

Library home page: https://github.com/MidnightBSD/src.git

Vulnerable Source Files (3)

/contrib/unbound/util/data/msgencode.c
/contrib/unbound/util/data/msgparse.c
/contrib/unbound/util/data/msgencode.h

src4.0.4

Library home page: https://github.com/MidnightBSD/src.git

Vulnerable Source Files (3)

/contrib/unbound/util/data/msgencode.c
/contrib/unbound/util/data/msgparse.c
/contrib/unbound/util/data/msgencode.h

Found in HEAD commit: 816463d989cc5839c1cca2efb5bf2503408507fb

Found in base branches: stable/4.0, master

Vulnerability Details

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.

Publish Date: 2026-05-20

URL: CVE-2026-42944

CVSS 3 Score Details (7.5)

Base Score Metrics:

• Exploitability Metrics:
  • Attack Vector: Network
  • Attack Complexity: Low
  • Privileges Required: None
  • User Interaction: None
  • Scope: Unchanged
• Impact Metrics:
  • Confidentiality Impact: None
  • Integrity Impact: None
  • Availability Impact: High

For more information on CVSS3 Scores, click here.

Suggested Fix

Type: Upgrade version

Release Date: 2026-05-20

Fix Resolution: https://github.com/NLnetLabs/unbound.git - release-1.25.1

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