Improper control of a resource through its lifetime in Unbound - CVE-2026-40622
Published: May 20, 2026
Vulnerability identifier: #VU131925
CSH Severity: Medium
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:U/U:Green
CVE-ID: CVE-2026-40622
CWE-ID: CWE-664
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: NLnet Labs
Affected software:
Unbound
Unbound
Detailed vulnerability description
The vulnerability allows a remote attacker to extend the ghost domain window.
The vulnerability exists due to improper handling of cached parent-side referral NS records in Unbound when processing NS queries for a ghost zone. A remote attacker can control a ghost zone and trigger replacement of an expired parent-side referral NS rrset with the child-side apex NS rrset to extend the ghost domain window.
In configurations with 'harden-referral-path: yes', no client NS query is required because the resolver performs that query implicitly.
How to mitigate CVE-2026-40622
Install security update from vendor's website.