CVE-2026-44621 (Medium) detected in multiple libraries

[mend-bolt-for-github]

CVE-2026-44621 - Medium 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/smallapp/worker_cb.c
/contrib/unbound/daemon/worker.c
/contrib/unbound/util/fptr_wlist.c

src4.0.4

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

Vulnerable Source Files (3)

/contrib/unbound/smallapp/worker_cb.c
/contrib/unbound/daemon/worker.c
/contrib/unbound/util/fptr_wlist.c

src4.0.4

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

Vulnerable Source Files (3)

/contrib/unbound/smallapp/worker_cb.c
/contrib/unbound/daemon/worker.c
/contrib/unbound/util/fptr_wlist.c

Found in HEAD commit: 816463d989cc5839c1cca2efb5bf2503408507fb

Found in base branches: stable/4.0, master

Vulnerability Details

With NLnet Labs Unbound up to and including version 1.25.1, applications using libunbound and configured with 'unwanted-reply-threshold', could eventually be abruptly terminated if the threshold is reached and libunbound needs to call 'libworker_alloc_cleanup' since the function is absent from the function call allow list. When an application using libunbound sets 'unwanted-reply-threshold' to any non-zero value and the iterator queries an authoritative that replies with enough wrong-transaction-ID UDP datagrams to cross the threshold, the 'libworker_alloc_cleanup' will eventually be called. Since the function is absent from the function call allow list, this leads to a fatal exit of libunbound and eventual termination of the embedding application.Unbound itself is not affected since its relevant function 'worker_alloc_cleanup' is registed in the allow list and proceeds to perform the documented cache flush.

Publish Date: 2026-07-22

URL: CVE-2026-44621

CVSS 3 Score Details (5.9)

Base Score Metrics:

• Exploitability Metrics:
  • Attack Vector: Network
  • Attack Complexity: High
  • 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: 2026-07-22

Fix Resolution: https://github.com/NLnetLabs/unbound.git - release-1.25.2

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