OnionShare is an open source tool that lets you securely and anonymously share files, host websites, and chat with friends using the Tor network. In affected versions the receive mode limits concurrent uploads to 100 per second and blocks other uploads in the same second, which can be triggered by a simple script. An adversary with access to the receive mode can block file upload for others. There is no way to block this attack in public mode due to the anonymity properties of the tor network.
The product does not properly control the allocation and maintenance of a limited resource.
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Onionshare | Onionshare | * | 2.5 (excluding) |
| Onionshare | Ubuntu | bionic | * |
| Onionshare | Ubuntu | esm-apps/focal | * |
| Onionshare | Ubuntu | esm-apps/jammy | * |
| Onionshare | Ubuntu | focal | * |
| Onionshare | Ubuntu | impish | * |
| Onionshare | Ubuntu | jammy | * |
| Onionshare | Ubuntu | lunar | * |
| Onionshare | Ubuntu | mantic | * |
| Onionshare | Ubuntu | trusty | * |
| Onionshare | Ubuntu | upstream | * |
| Onionshare | Ubuntu | xenial | * |
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.