When using forwarders in BIND, bogus NS records supplied by, or via, those forwarders may be cached and used by named if it needs to recurse for any reason, causing it to obtain and pass on potentially incorrect answers. The cache could become poisoned with incorrect records leading to queries being made to the wrong servers, which might also result in false information being returned to clients. Authoritative-only BIND 9 servers are not vulnerable to this flaw.
When using forwarders in BIND, bogus NS records supplied by, or via, those forwarders may be cached and used by named if it needs to recurse for any reason, causing it to obtain and pass on potentially incorrect answers. The cache could become poisoned with incorrect records leading to queries being made to the wrong servers, which might also result in false information being returned to clients. Authoritative-only BIND 9 servers are not vulnerable to this flaw.
https://kb.isc.org/docs/cve-2021-25220 https://gitlab.isc.org/isc-projects/bind9/-/commit/fc9cb6cf91c1a36b797ffef0a277dbb3989d43dc
Workarounds: If applicable, modify your configuration to either remove all forwarding or all possibility of recursion. Depending on your use-case, it may be possible to use other zone types to replace forward zones.
Vulmon