The lame-ttl option controls how long named caches certain types of
broken responses from authoritative servers (see the security advisory
for details). This caching mechanism could be abused by an attacker to
significantly degrade resolver performance. The vulnerability has been
mitigated by changing the default value of lame-ttl to 0 and overriding
any explicitly set value with 0, effectively disabling this mechanism
altogether. ISC's testing has determined that doing that has a
negligible impact on resolver performance while also preventing abuse.
Administrators may observe more traffic towards servers issuing certain
types of broken responses than in previous BIND 9 releases, depending on
client query patterns. (CVE-2021-25219)
ISC would like to thank Kishore Kumar Kothapalli of Infoblox for
bringing this vulnerability to our attention. [GL #2899]
Signed-off-by: Ralph Siemsen <ralph.siemsen@linaro.org> Signed-off-by: Steve Sakoman <steve@sakoman.com>
