An issue was discovered in the default FilterScheduler in OpenStack Nova 16.0.3. By repeatedly rebuilding an instance with new images, an authenticated user may consume untracked resources on a hypervisor host leading to a denial of service, aka doubled resource allocations. This regression was introduced with the fix for OSSA-2017-005 (CVE-2017-16239); however, only Nova stable/pike or later deployments with that fix applied and relying on the default FilterScheduler are affected.
The product does not properly control the allocation and maintenance of a limited resource.
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Nova | Openstack | 16.0.3 (including) | 16.0.3 (including) |
| Nova | Ubuntu | artful | * |
| Nova | Ubuntu | zesty | * |
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.