CVE-2026-44608
Use after free and crash under special conditions in RPZ code
Description
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.
INFO
Published Date :
May 20, 2026, 10:16 a.m.
Last Modified :
July 24, 2026, 10:10 a.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 3.1 | MEDIUM | [email protected] | ||||
| CVSS 4.0 | MEDIUM | 206fc3a0-e175-490b-9eaa-a5738056c9f6 | ||||
| CVSS 4.0 | MEDIUM | [email protected] |
Solution
- Update Unbound to version 1.25.1 or later.
- Apply the vendor-provided patch for the locking code.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-44608.
| URL | Resource |
|---|---|
| https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-44608.txt | Mitigation Vendor Advisory |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-44608 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-44608
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-44608 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-44608 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
CVE Translated by [email protected]
Jul. 24, 2026
Action Type Old Value New Value Added Translation Title: Unbound de NLnet Labs, Description: NLnet Labs Unbound 1.14.0 hasta e incluyendo la versión 1.25.0 tiene una vulnerabilidad de inconsistencia de bloqueo que, cuando se cumplen ciertas condiciones (multihilo, recarga de RPZ XFR, zona RPZ con disparadores 'rpz-nsip'/'rpz-nsdname'), podría resultar en un uso después de liberación de la pila y un fallo eventual. Un adversario puede explotar la vulnerabilidad si primero se cumplen las condiciones en un Unbound vulnerable, es decir, multihilo, una zona RPZ con disparadores 'rpz-nsip'/'rpz-nsdname' y un XFR en curso para esa zona RPZ. Los archivos RPZ locales no disparan la vulnerabilidad. Si el momento es el adecuado y un XFR ocurre al mismo tiempo que otro hilo necesita leer esa zona RPZ, el lector podría no mantener el bloqueo el tiempo suficiente y el hilo que aplica el XFR podría liberar objetos que el lector está a punto de recorrer, causando el uso después de liberación. Unbound 1.25.1 contiene un parche con una corrección para el código de bloqueo. -
CVE Modified by [email protected]
Jun. 17, 2026
Action Type Old Value New Value Added Affected [{'vendor': 'NLnet Labs', 'product': 'Unbound', 'versions': [{'status': 'affected', 'version': '1.14.0', 'lessThan': '1.25.1', 'versionType': 'semver'}], 'defaultStatus': 'unaffected'}] -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Jun. 17, 2026
Action Type Old Value New Value Added SSVC {'id': 'CVE-2026-44608', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'none'}, {'automatable': 'no'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-05-20T12:46:59.939210Z'} -
Initial Analysis by [email protected]
May. 20, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H Added CPE Configuration OR *cpe:2.3:a:nlnetlabs:unbound:*:*:*:*:*:*:*:* versions from (including) 1.14.0 up to (excluding) 1.25.1 Added Reference Type NLnet Labs: https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-44608.txt Types: Mitigation, Vendor Advisory -
New CVE Received by [email protected]
May. 20, 2026
Action Type Old Value New Value Added Description 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. Added CVSS V4.0 AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:Amber Added CWE CWE-413 Added Reference https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-44608.txt