Unbound before 1.9.5 allows an assertion failure and denial of service in synth_cname. NOTE: The vendor disputes that this is a vulnerability. Although the code may be vulnerable, a running Unbound installation cannot be remotely or locally exploited
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 |
|---|---|---|---|
| Unbound | Nlnetlabs | * | 1.9.5 (excluding) |
| Red Hat Enterprise Linux 8 | RedHat | unbound-0:1.7.3-15.el8 | * |
| Red Hat Enterprise Linux 8.2 Extended Update Support | RedHat | unbound-0:1.7.3-12.el8_2 | * |
| Unbound | Ubuntu | bionic | * |
| Unbound | Ubuntu | focal | * |
| Unbound | Ubuntu | trusty | * |
| Unbound | Ubuntu | upstream | * |
| Unbound | 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.