CVE-2026-44608Network attack vector

Daemon crash via RPZ reload locking race

Published May 20, 2026 · Updated May 20, 2026

Improper resource locking in NLnet Labs Unbound 1.14.0 through 1.25.0 allows remote attackers to crash the DNS resolver via RPZ XFR activity. During an XFR reload of an RPZ zone using rpz-nsip or rpz-nsdname triggers, a reader releases the RPZ lock before finishing its walk while the reload thread frees objects it is about to access. Exploitation requires multithreading, the affected RPZ triggers, an ongoing network-transferred zone reload, and favorable timing; local RPZ files do not expose the race, and the bounded result is a daemon crash.

CVSS severity5.9
Medium
EPSS probability0.26%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper resource locking in NLnet Labs Unbound 1.14.0 through 1.25.0 allows remote attackers to crash the DNS resolver via RPZ XFR activity. During an XFR reload of an RPZ zone using rpz-nsip or rpz-nsdname triggers, a reader releases the RPZ lock before finishing its walk while the reload thread frees objects it is about to access. Exploitation requires multithreading, the affected RPZ triggers, an ongoing network-transferred zone reload, and favorable timing; local RPZ files do not expose the race, and the bounded result is a daemon crash.

The record

CVE
CVE-2026-44608
Published
May 20, 2026
Updated
May 20, 2026
Vendor
NLnet Labs
Product
Unbound
Classifications
CWE-413, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 20, 2026CVE publishedPublication date reported by the CVE source.
  2. May 20, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=1.14.0 <1.25.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

NLnet Labs · Unboundversion=1.14.0 <1.25.1

Published CVSS scores

5.9NIST NVDCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
4.6NLnet LabsCVSS: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

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-413Improper Resource Locking
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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