A Reachable Assertion issue was discovered in the KDC in MIT Kerberos 5 (aka krb5) before 1.17. If an attacker can obtain a krbtgt ticket using an older encryption type (single-DES, triple-DES, or RC4), the attacker can crash the KDC by making an S4U2Self request.
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 |
|---|---|---|---|
| Kerberos | Mit | * | 5-1.17 (excluding) |
| Red Hat Ansible Tower 3.4 for RHEL 7 | RedHat | ansible-tower-34/ansible-tower-memcached:1.4.15-28 | * |
| Red Hat Ansible Tower 3.4 for RHEL 7 | RedHat | ansible-tower-35/ansible-tower-memcached:1.4.15-28 | * |
| Red Hat Ansible Tower 3.4 for RHEL 7 | RedHat | ansible-tower-37/ansible-tower-memcached-rhel7:1.4.15-28 | * |
| Red Hat Enterprise Linux 7 | RedHat | krb5-0:1.15.1-37.el7_7.2 | * |
| Krb5 | Ubuntu | bionic | * |
| Krb5 | Ubuntu | cosmic | * |
| Krb5 | Ubuntu | disco | * |
| Krb5 | Ubuntu | eoan | * |
| Krb5 | Ubuntu | esm-infra/xenial | * |
| Krb5 | Ubuntu | precise/esm | * |
| Krb5 | Ubuntu | trusty | * |
| Krb5 | Ubuntu | trusty/esm | * |
| Krb5 | Ubuntu | upstream | * |
| Krb5 | 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.