Use-after-free in Unbound - CVE-2026-50046
Published: July 23, 2026
Vulnerability identifier: #VU139231
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-2026-50046
CWE-ID: CWE-416
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 a use-after-free in the DNS-over-TLS forwarding logic when handling forwarded queries during TLS handshake error paths. A remote attacker can query records in the appropriate zone while keeping the daemon under pressure to trigger the vulnerable error path and cause a denial of service.
Exploitation requires a stub or forward zone configured for DNS-over-TLS together with a configured authname suffix on the server identification, and transient connectivity failure at a precise time during the handshake.
How to mitigate CVE-2026-50046
Install security update from vendor's website.