CVE-2026-11331

A flaw was found in BIND. A remote attacker can send specially crafted, excessively long query names to a resolver configured with Response Policy Zones (RPZ) and wildcard policies. Improper handling of the resulting error condition can cause the service to terminate unexpectedly, leading to a Denial of Service (DoS), or allow the attacker to bypass RPZ security filtering rules.

This vulnerability is rated as Important because an unauthenticated remote client can terminate the DNS resolver service or bypass security filtering policies. In default Red Hat Enterprise Linux installations, Response Policy Zones (RPZ) are not configured and require explicit administrative definition. The flaw poses operational risk primarily to recursive resolvers that actively employ wildcard CNAME rules in their policy zones and accept untrusted network queries.

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, restrict resolver access to trusted networks and avoid using wildcard CNAME entries within Response Policy Zones (RPZ).

1. Edit /etc/named.conf to limit recursion and query caching to authorized client networks:

acl trusted_clients {
    127.0.0.1;
    192.168.1.0/24;
};

options {
    allow-recursion { trusted_clients; };
    allow-query-cache { trusted_clients; };
};

Additionally, modify RPZ zone files to remove wildcard CNAME statements (such as *.example.com CNAME target.com), replacing them with explicit individual domain entries where feasible.

2. Reload the named service configuration: systemctl reload named

Caveats: Restricting query access prevents untrusted external clients from resolving names through the server. Removing wildcard entries means unlisted subdomains will no longer be intercepted by the policy zone until explicit records are added.

Warning: Reloading or restarting the named daemon may briefly disrupt ongoing DNS resolution.