A vulnerability in the WebVPN login process of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause increased CPU utilization on an affected device. The vulnerability is due to excessive processing load for existing WebVPN login operations. An attacker could exploit this vulnerability by sending multiple WebVPN login requests to the device. A successful exploit could allow the attacker to increase CPU load on the device, resulting in a denial of service (DoS) condition.
Weakness
The product does not properly control the allocation and maintenance of a limited resource.
Affected Software
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Adaptive_security_appliance_software | Cisco | * | 9.4.4.34 (excluding) |
| Adaptive_security_appliance_software | Cisco | 9.5 (including) | 9.6.4.25 (excluding) |
| Adaptive_security_appliance_software | Cisco | 9.7 (including) | 9.8.4 (excluding) |
| Adaptive_security_appliance_software | Cisco | 9.9 (including) | 9.9.2.50 (excluding) |
Potential Mitigations
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.
Related Attack Patterns
- https://cwe.mitre.org/data/definitions/147.html
- https://cwe.mitre.org/data/definitions/227.html
- https://cwe.mitre.org/data/definitions/492.html