CVE-2026-13204: ISC BIND 9

High severity, CVSS 7.5. EPSS: 0.5% chance of exploitation in the next 30 days.

If a provably insecure domain is covered by both an NSEC and NSEC3 record at the parent, and there exist an RRSIG for only one of these types, then BIND may exit unexpectedly with an assertion while validating this proof. This issue affects BIND 9 versions 9.11.0 through 9.18.50, 9.20.0 through 9.20.24, 9.21.0 through 9.21.23, 9.11.3-S1 through 9.18.50-S1, and 9.20.9-S1 through 9.20.24-S1.

Affected products

• ISC BIND 9: from 9.11.0, up to and including 9.18.50; from 9.20.0, up to and including 9.20.24; from 9.21.0, up to and including 9.21.23; from 9.11.3-S1, up to and including 9.18.50-S1; from 9.20.9-S1, up to and including 9.20.24-S1

Published 2026-07-22. Last modified 2026-07-22.