Improper control of a resource through its lifetime in Unbound - CVE-2026-42534
Published: May 20, 2026
Vulnerability identifier: #VU131927
CSH Severity: Low
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Clear
CVE-ID: CVE-2026-42534
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 cause a denial of service.
The vulnerability exists due to improper state management in Unbound jostle logic when processing duplicate queries while resolving queries through a slow or malicious authoritative name server. A remote user can send repeated queries for names served by a controlled slow-responding domain name server to cause a denial of service.
Cache and local data response performance remains unaffected. Exploitation requires the resolver to reach its configured query-per-thread limit, and coordinated attacks can degrade resolution into denial of resolution service.
How to mitigate CVE-2026-42534
Install security update from vendor's website.