An inapplicable NSEC record may be accepted by a named resolver as proof that no wildcard exists, which could allow an attacker at the same or an upstream level of the zone name to mask the existence of a victim's wildcard record.
This issue affects BIND 9 versions 9.11.0 through 9.18.50, 9.20.0 through 9.20.27, 9.21.0 through 9.21.25, 9.11.3-S1 through 9.18.50-S1, and 9.20.9-S1 through 9.20.27-S1.
Exploitability
AV:NAC:HPR:NUI:NScope
S:UImpact
C:NI:HA:N5.9/CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:NOther