Improper control of a resource through its lifetime in Unbound - CVE-2026-42955
Published: July 23, 2026
Vulnerability identifier: #VU139237
CSH Severity: Low
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:U/U:Clear
CVE-ID: CVE-2026-42955
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 user to extend the ghost domain window.
The vulnerability exists due to improper cache handling in the handling of cached parent-side A/AAAA glue rrsets when processing A/AAAA queries for a ghost zone. A remote user can trigger a client A/AAAA query to extend the ghost domain window.
Exploitation requires control of a ghost zone and the ability to query a vulnerable resolver. In configurations with 'harden-referral-path: yes' enabled, no client query is required because the resolver performs the query implicitly.
How to mitigate CVE-2026-42955
Install security update from vendor's website.