When adding an external mail account, processing of SMTP capabilities responses are not limited to plausible sizes. Attacker with access to a rogue SMTP service could trigger requests that lead to excessive resource usage and eventually service unavailability. We now limit accepted SMTP server response to reasonable length/size. No publicly available exploits are known.
The product does not properly control the allocation and maintenance of a limited resource.
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Open-xchange_appsuite_backend | Open-xchange | * | 7.10.6 (excluding) |
| Open-xchange_appsuite_backend | Open-xchange | 8.0.0 (including) | 8.11.0 (excluding) |
| Open-xchange_appsuite_backend | Open-xchange | 7.10.6 (including) | 7.10.6 (including) |
| Open-xchange_appsuite_backend | Open-xchange | 7.10.6-revision_39 (including) | 7.10.6-revision_39 (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.