CVE-2026-44608

NLnet Labs Unbound 1.14.0 up to and including version 1.25.0 has a locking inconsistency vulnerability that when certain conditions are met (multi-threaded, RPZ XFR reload, RPZ zone with 'rpz-nsip'/'rpz-nsdname' triggers) it could result in heap use-after-free and eventual crash. An adversary can exploit the vulnerability if conditions are first met on a vulnerable Unbound, i.e., multi-threaded, an RPZ zone with 'rpz-nsip'/'rpz-nsdname' triggers and an ongoing XFR for that RPZ zone. Local RPZ files do not trigger the vulnerability. If the timing is right and an XFR happens at the same time another thread needs to read that RPZ zone, the reader may not hold the lock long enough and the thread applying the XFR may free objects that the reader is about to walk causing the use-after-free. Unbound 1.25.1 contains a patch with a fix to the locking code.

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-2026-44608.txt	Mitigation Vendor Advisory

Configurations

Configuration 1 (hide)

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

History

20 May 2026, 22:52

Type	Values Removed	Values Added
First Time		Nlnetlabs Nlnetlabs unbound
CPE		cpe:2.3:a:nlnetlabs:unbound::::::::
CVSS	v2 : ~~unknown~~ v3 : ~~unknown~~	v2 : unknown v3 : 5.9
References	~~() https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-44608.txt -~~	() https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-44608.txt - Mitigation, Vendor Advisory

20 May 2026, 10:16

Type	Values Removed	Values Added
New CVE

Information

Published : 2026-05-20 10:16

Updated : 2026-05-20 22:52

NVD link : CVE-2026-44608

Mitre link : CVE-2026-44608

CVE.ORG link : CVE-2026-44608

JSON object : View

Products Affected

nlnetlabs

unbound

CWE

CWE-413

Improper Resource Locking

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