Access of Uninitialized Pointer in Unbound - CVE-2026-42959
Published: May 20, 2026
Vulnerability identifier: #VU131930
CSH Severity: Medium
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Green
CVE-ID: CVE-2026-42959
CWE-ID: CWE-824
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 cause a denial of service.
The vulnerability exists due to use of an uninitialized pointer in the DNSSEC validator when constructing chase-reply messages for validation. A remote attacker can provide a malicious upstream reply to cause a denial of service.
Exploitation requires control of a DNSSEC-signed domain and can be triggered with a single query using a DNAME chain with unsigned CNAMEs and a response containing unsigned AUTHORITY records alongside signed ADDITIONAL glue records.
How to mitigate CVE-2026-42959
Install security update from vendor's website.