CVE-2026-11331 ISC CVE debrief

Who should care

Organizations using BIND 9 with RPZ and wildcard CNAME policies should assess their vulnerability and apply patches or mitigations. This includes reviewing and updating RPZ configurations, monitoring BIND 9 logs for unusual query patterns or error conditions, and considering additional security controls such as query rate limiting or IP blocking.

Technical summary

The vulnerability allows an attacker to craft query names that trigger a NAMETOOLONG error during RPZ processing, potentially defeating RPZ rules or causing the BIND 9 software to exit unexpectedly. Affected versions include 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. The issue arises when an attacker knows or guesses that a resolver uses RPZ with wildcard CNAME policies and crafts query names long enough to trigger a NAMETOOLONG error condition during RPZ processing.

Defensive priority

High

Recommended defensive actions

• Inventory BIND 9 installations and versions to identify potentially vulnerable configurations.
• Apply patches or updates to affected BIND 9 versions.
• Review and update RPZ configurations to reduce the risk of exploitation.
• Monitor BIND 9 logs for unusual query patterns or error conditions.
• Consider implementing additional security controls, such as query rate limiting or IP blocking.

Evidence notes

The CVE record was published on 2026-07-22T15:16:51.457Z and was last modified on 2026-07-22T20:33:11.590Z. The NVD entry is currently Awaiting Analysis. This information is based on the provided source corpus. Further verification is recommended to confirm the accuracy of this information.

Official resources