Client queries that trigger serving stale data and that also require lookups in local authoritative zone data may result in an assertion failure. This issue affects BIND 9 versions 9.16.13 through 9.16.50, 9.18.0 through 9.18.27, 9.19.0 through 9.19.24, 9.11.33-S1 through 9.11.37-S1, 9.16.13-S1 through 9.16.50-S1, and 9.18.11-S1 through 9.18.27-S1.