High [CVE-2026-11331] Potential wildcard CNAME RPZ policy bypass
This high-severity Red Hat Linux advisory covers CVE-2026-11331 affecting Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support, Red Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-On.
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Summary
An attacker who knows (or guesses) that a resolver uses RPZ with wildcard CNAME policies can craft query names long enough to trigger a NAMETOOLONG error condition during RPZ processing. This is not handled correctly and may lead to defeating the RPZ rule.
It also may lead to an unexpected exit of the BIND 9 software. This issue affects BIND 9 versions 9.16.0 through 9.18.50, 9.20.0 through 9.20.24, 9.21.0 through 9.21.23, 9.16.8-S1 through 9.18.50-S1, and 9.20.9-S1 through 9.20.24-S1.
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.
- 9.16.0
- 9.18.50
- 9.20.0
- 9.20.24
- 9.21.0
- 9.21.23
- 9.16.8
- 9.20.9
Official advisory · high-confidence parse· fetched 1 day ago·verify at source
- bind-32:9.18.33-15.el10_2.10
- bind9.16-32:9.16.23-0.22.el8_10.12
- bind9.16-32:9.16.23-0.7.el8_6.11
- bind9.16-32:9.16.23-0.14.el8_8.9
- bind-32:9.16.23-40.el9_8.8
- bind9.18-32:9.18.29-14.el9_8.8
- bind-32:9.16.23-18.el9_4.12
- bind-32:9.16.23-31.el9_6.4
- openshift/ose-rhel-coreos-9:416.94.202609011112-0
- openshift/ose-rhel-coreos-9:417.94.202609191027-0
- openshift/ose-rhel-coreos-9:418.94.202609031320-0
- openshift/ose-rhel-coreos-9:418.94.202609171815-0
- openshift/ose-rhel-coreos-9:4.22.9.8.202608251819-0
- bind-main-9.20.26-0.1.hum1
- RHSA-2026:55437
- RHSA-2026:54509
- RHSA-2026:80501
- RHSA-2026:79160
- RHSA-2026:54510
- RHSA-2026:55442
- RHSA-2026:57189
- RHSA-2026:55441
- RHSA-2026:62549
- RHSA-2026:70586
- RHSA-2026:65851
- RHSA-2026:70615
- RHSA-2026:60440
- RHSA-2026:54071
Official advisory · high-confidence parse· fetched 1 day ago·verify at source
Mitigation checklist
- 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.
Official advisory · high-confidence parse· fetched 1 day ago·verify at source
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