Assemblyline 4 Service Client: Arbitrary Write through path traversal in Client code

Vulnerability Description

The Assemblyline 4 Service Client interfaces with the API to fetch tasks and publish the result for a service in Assemblyline 4. In versions below 4.6.1.dev138, the Assemblyline 4 Service Client (task_handler.py) accepts a SHA-256 value returned by the service server and uses it directly as a local file name.A malicious or compromised server (or any MITM that can speak to client) can return a path-traversal payload such as `../../../etc/cron.d/evil` and force the client to write the downloaded bytes to an arbitrary location on disk. This is fixed in version 4.6.1.dev138.

References

• https://github.com/CybercentreCanada/assemblyline/security/advisories/GHSA-75jv-vfxf-3865
• https://github.com/CybercentreCanada/assemblyline-service-client/commit/351414e7e96cc1f5640ae71ae51b939e8ba30900