Zimbra Collaboration (ZCS) before 9.0.0 Patch 46, 10.0.x before 10.0.15, and 10.1.x before 10.1.9 is vulnerable to a denial of service condition due to improper handling of excessive, comma-separated path segments in the Admin Console. An unauthenticated remote attacker can send specially crafted GET requests that trigger redundant processing and inflated responses. This leads to uncontrolled resource consumption, resulting in denial of service.
The product does not properly control the allocation and maintenance of a limited resource.
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.