Processing of repeated responses to the same query, where both responses contain ECS pseudo-options, but where the first is broken in some way, can cause BIND to exit with an assertion failure.
Broken in this context is anything that would cause the resolver to reject the query response, such as a mismatch between query and answer name. This issue affects BIND 9 versions 9.11.4-S1 through 9.11.37-S1 and 9.16.8-S1 through 9.16.36-S1.
The product contains an assert() or similar statement that can be triggered by an attacker, which leads to an application exit or other behavior that is more severe than necessary.
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Bind | Isc | 9.11.4-s1 (including) | 9.11.4-s1 (including) |
| Bind | Isc | 9.11.37-s1 (including) | 9.11.37-s1 (including) |
| Bind | Isc | 9.16.8-s1 (including) | 9.16.8-s1 (including) |
| Bind | Isc | 9.16.36-s1 (including) | 9.16.36-s1 (including) |
| Bind9 | Ubuntu | trusty | * |
| Bind9 | Ubuntu | xenial | * |
While assertion is good for catching logic errors and reducing the chances of reaching more serious vulnerability conditions, it can still lead to a denial of service. For example, if a server handles multiple simultaneous connections, and an assert() occurs in one single connection that causes all other connections to be dropped, this is a reachable assertion that leads to a denial of service.