Improper access control in Unbound - CVE-2026-44621
Published: July 23, 2026
Vulnerability identifier: #VU139236
CSH Severity: Medium
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Green
CVE-ID: CVE-2026-44621
CWE-ID: CWE-284
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 improper access control in the libworker_alloc_cleanup function call allow list in libunbound when processing enough wrong-transaction-ID UDP replies to cross the unwanted-reply-threshold. A remote attacker can send crafted UDP replies to cause a denial of service.
Only applications using libunbound with 'unwanted-reply-threshold' set to a non-zero value are vulnerable. Unbound itself is not affected.
How to mitigate CVE-2026-44621
Install security update from vendor's website.