CVE-2026-82720

A use-after-free vulnerability in Unbound's DNS-over-HTTPS (DoH) stream cleanup code allows a remote attacker to cause a denial of service (DoS). When DoH support is compiled, sending a specially crafted DoH connection under specific failure conditions—such as an RPZ drop query or heavy traffic—causes the Unbound process to terminate.

This Moderate impact use-after-free vulnerability in Unbound, when configured with DNS-over-HTTPS (DoH) support, can lead to a denial of service. The flaw occurs during specific failure conditions like RPZ drops or heavy traffic, causing the Unbound process to terminate. While direct user control over reads is limited, the vulnerability can still disrupt service in affected Red Hat products where Unbound is compiled with DoH support.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

To mitigate this issue, disable DNS-over-HTTPS (DoH) support in Unbound if it is not required. This can typically be achieved by commenting out or removing the do-https: configuration block in the unbound.conf file and restarting the Unbound service. Disabling DoH may affect clients relying on this protocol for DNS resolution. A service restart is required for the changes to take effect.