An issue was discovered on FiberHome Fengine S5800 switches V210R240. An unauthorized attacker can access the devices SSH service, using a password cracking tool to establish SSH connections quickly. This will trigger an increase in the SSH login timeout (each of the login attempts will occupy a connection slot for a longer time). Once this occurs, legitimate login attempts via SSH/telnet will be refused, resulting in a denial of service; you must restart the device.
The product does not properly control the allocation and maintenance of a limited resource.
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Fengine_s5800_firmware | Fiberhome | v210r240 (including) | v210r240 (including) |
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.