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CVE-2026-44608

28
FAUCET Score

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.

First published: May 20, 2026Last modified: May 20, 2026

Impacted Technologies

VendorProductVersion(s)CPE
>= 1.14.0, < 1.25.1CPE matchmatch criteria
cpe:2.3:a:nlnetlabs:unbound:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 4.0

4.6MEDIUM

CVSS:4.0/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

Attack Vector
NETWORK
Attack Complexity
HIGH
Attack Requirements
PRESENT
Privileges Required
NONE
User Interaction
NONE
VS Confidentiality
NONE
VS Integrity
NONE
VS Availability
HIGH
SS Confidentiality
NONE
SS Integrity
NONE
SS Availability
NONE
Exploit Maturity
UNREPORTED
CvssVersion
4.0

Exploit Intelligence

EPSS Score
0.26%
Probability of exploitation in next 30 days
EPSS Percentile
17.1%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0026 is in the 2nd percentile among its peer group of 19,958 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.0 Bluesky, 0.0 Mastodon, and 0.2 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.0 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (6)

microsoftpatch availablevia msrc
Product: 20736-17084Fixed in: 1.25.1-1
microsoftpatch availablevia msrc
Product: azl3 unbound 1.19.1-5 on Azure Linux 3.0Fixed in: 1.25.1-1
ubuntupatch availablevia ubuntu_usn
Product: unbound (jammy)Fixed in: 1.13.1-1ubuntu5.15
ubuntupatch availablevia ubuntu_usn
Product: unbound (noble)Fixed in: 1.19.2-1ubuntu3.8
ubuntupatch availablevia ubuntu_usn
Product: unbound (questing)Fixed in: 1.22.0-2ubuntu2.3
ubuntupatch availablevia ubuntu_usn
Product: unbound (resolute)Fixed in: 1.24.2-1ubuntu2.1

Vendor Advisories (2)

ubuntuUSN-8282-1

Unbound vulnerabilities

May 20, 2026
microsoft2026-May/CVE-2026-44608Moderate

Use after free and crash under special conditions in RPZ code

May 12, 2026

References

nlnetlabs.nl / downloads/unbound/CVE-2026-44608.txt
MitigationVendor Advisory