Pickle in the Middle – Hijacking Vertex AI Model Uploads for Cross-Tenant RCE

Researchers discovered a vulnerability in Google Cloud's Vertex AI SDK for Python (versions 1.139.0 and 1.140.0) that allowed attackers to hijack model uploads through bucket squatting (exploiting predictable cloud storage bucket names to intercept files). By predicting the victim's bucket name based on their project ID, an attacker could create that bucket in their own account, intercept the model upload, inject malicious code, and achieve RCE (remote code execution, where attackers run commands on systems they don't own) when the victim deployed the poisoned model.