CVE-2026-44621

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.

CVSS v3 5.9 MEDIUM

5.9^/10

CVSS v3 : MEDIUM

Vector :

Exploitability : 2.2 / Impact : 3.6

Attack Vector NETWORK

Attack Complexity HIGH

Privileges Required NONE

User Interaction NONE

Confidentiality Impact NONE

Integrity Impact NONE

Availability Impact HIGH

Scope UNCHANGED

References

Link	Resource
https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-44621.txt	Vendor Advisory

Configurations

Configuration 1 (hide)

cpe:2.3:a:nlnetlabs:unbound:*:*:*:*:*:*:*:*

History

24 Jul 2026, 13:56

Type	Values Removed	Values Added
CPE		cpe:2.3:a:nlnetlabs:unbound::::::::
First Time		Nlnetlabs Nlnetlabs unbound
References	~~() https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-44621.txt -~~	() https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-44621.txt - Vendor Advisory

22 Jul 2026, 14:17

Type	Values Removed	Values Added
New CVE

Information

Published : 2026-07-22 14:17

Updated : 2026-07-24 13:56

NVD link : CVE-2026-44621

Mitre link : CVE-2026-44621

CVE.ORG link : CVE-2026-44621

JSON object : View

Products Affected

nlnetlabs

unbound

CWE

CWE-754

Improper Check for Unusual or Exceptional Conditions

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