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CVE-2026-44608

đŸ”ļ medium
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Summary

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 fi

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.

CVSS Score
5.9
Medium
EPSS Score
0.3
Exploit Probability
Published Date
2026-05-20
First Seen: 2026-05-21
📊 Relative Risk Intelligence

This CVE is Lower Risk - more severe than 32.4% of all 349,016 vulnerabilities in our database.

#236,063
Below average severity
Severity Percentile
đŸŽ¯ CISA SSVC Assessment Updated: May 20, 2026
🔍 Exploitation Status
None
No known exploits
⚙ī¸ Automatable
NO
Requires human interaction
đŸ’Ĩ Technical Impact
Partial
Limited system impact
🏆 Discovered By
Qifan Zhang (Palo Alto Networks)
SSVC data provided by CISA
Last Modified 2026-07-24
Source NVD 🔗
CVSS Vector 3.1 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
CVSS Vector 4.0 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
CWE IDs (Weakness Types)
CWE-413

đŸ“Ļ Affected Products 1

Vendor Product Status Affected Versions
nlnetlabs unbound Affected
> 1.14.0 < 1.25.1

🔗 References 1

https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-...
Mitigation Vendor Advisory

🔗 Related CVEs 6

CVE ID Severity CVSS EPSS Summary Published
CVE-2026-32665 ⚠ī¸ high 7.5 0.3 In NLnet Labs Unbound 1.22.0 up to and including 1.25.1, when downstream DNS-over-QUIC (DoQ) is enabled, the first two b... 2026-07-22
CVE-2026-40691 ⚠ī¸ high 7.5 0.3 In Unbound 1.9.0 up to and including 1.25.1, when a DNSCrypt query is received over TCP, the routine that encrypts the r... 2026-07-22
CVE-2026-41637 ℹī¸ low 3.7 0.3 In NLnet Labs Unbound 1.22.0 up to and including 1.25.1, client terminated DNS-over-QUIC (DoQ) queries are not accounted... 2026-07-22
CVE-2026-42955 ℹī¸ low 3.7 0.2 In NLnet Labs Unbound 1.16.2 up to and including 1.25.1, a similar vulnerability as with CVE-2026-40622 in the 'ghost do... 2026-07-22
CVE-2026-44621 đŸ”ļ medium 5.9 0.3 With NLnet Labs Unbound up to and including version 1.25.1, applications using libunbound and configured with 'unwanted-... 2026-07-22
CVE-2026-44687 ℹī¸ low 3.7 0.2 In NLnet Labs Unbound 1.13.2 up to and including 1.25.1, stub or forward zones where the name is below an intermediate l... 2026-07-22
These CVEs affect the same products