No Limit on Number of Open Sessions / Bad Session Close Behaviour in dnf5daemon-server before 5.1.17 allows a malicious user to impact Availability via No Limit on Number of Open Sessions.
There is no limit on how many sessions D-Bus clients may create using the open_session() D-Bus method. For each session a thread is created in dnf5daemon-server. This spends a couple of hundred megabytes of memory in the process. Further connections will become impossible, likely because no more threads can be spawned by the D-Bus service.
The product does not properly control the allocation and maintenance of a limited resource.
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Dnf5 | Rpm-software-management | * | 5.1.17 (excluding) |
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.