CVE-2026-52863

A flaw was found in Unbound, a validating, recursive, and caching Domain Name System (DNS) resolver. When configured with specific modules and under heavy load, a memory corruption vulnerability can occur due to improper handling of view names during subquery processing. This issue could lead to a denial of service (DoS) by causing the Unbound server to crash.

This Moderate flaw in Unbound arises from memory corruption under specific, non-default configurations involving 'respip' or 'rpz' modules, subquery attachment, and 'access-control-view' when the server is under heavy load. The likelihood of a crash is low due to reliance on memory allocator behavior, but it could lead to a denial of service.

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, avoid configuring Unbound with a combination of 'respip' or 'rpz' modules, subquery attachment features (such as respip CNAME redirection, dns64, or subnetcache), and 'access-control-view' if these functionalities are not strictly required. Disabling these specific configurations will prevent the conditions under which memory corruption can occur. Any changes to Unbound's configuration will require a service restart to take effect, which may temporarily interrupt DNS resolution services.