For a secondary zone with transfers restricted by TSIG, named may start to serve the data provided in a zone transfer before the final message with the TSIG signature arrives. This could allow an attacker that does not actually possess a valid TSIG signature to send unauthorized zone contents to a secondary server. Although no TSIG signature ever arrives, named does not rollback to the pre-transfer state. To exploit the vulnerability, the transfer must be a multi-message TCP IXFR, as described by RFC 8945.
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:L6.5/CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:LOther