An issue was discovered in Asterisk through 19.x. When using STIR/SHAKEN, it is possible to download files that are not certificates. These files could be much larger than what one would expect to download, leading to Resource Exhaustion. This is fixed in 16.25.2, 18.11.2, and 19.3.2.
The product does not properly control the allocation and maintenance of a limited resource.
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Asterisk | Digium | 16.15.0 (including) | 16.25.1 (including) |
| Asterisk | Digium | 18.0 (including) | 18.11.2 (excluding) |
| Asterisk | Digium | 19.0.0 (including) | 19.3.1 (including) |
| Asterisk | Ubuntu | bionic | * |
| Asterisk | Ubuntu | focal | * |
| Asterisk | Ubuntu | impish | * |
| Asterisk | Ubuntu | kinetic | * |
| Asterisk | Ubuntu | lunar | * |
| Asterisk | Ubuntu | mantic | * |
| Asterisk | Ubuntu | oracular | * |
| Asterisk | Ubuntu | trusty | * |
| Asterisk | Ubuntu | upstream | * |
| Asterisk | Ubuntu | xenial | * |
Mitigation of resource exhaustion attacks requires that the target system either:
The first of these solutions is an issue in itself though, since it may allow attackers to prevent the use of the system by a particular valid user. If the attacker impersonates the valid user, they may be able to prevent the user from accessing the server in question.
The second solution is simply difficult to effectively institute – and even when properly done, it does not provide a full solution. It simply makes the attack require more resources on the part of the attacker.