A flaw in the session assignment endpoint allows an authenticated attacker who discovers another user's session ID to take control of that session, read any exchanged messages, and prevent the legitimate user from re‑joining. The issue comes from the service layer invoking a privileged session lookup without verifying that the caller owns the session, which is a classic IDOR weakness (CWE‑862). The compromise enables confidentiality violations and denial of service for affected users.

Versions 0.6.36 through 0.6.50 of Significant Gravitas AutoGPT are affected. The vulnerability was remedied in version 0.6.51 and later.

The CVSS score of 7.1 indicates a substantial medium‑to‑high risk. EPSS is not available and the issue is not listed in the CISA KEV catalog. An attacker must already be authenticated and must discover a valid session ID; no additional privileges or public exploitation are required. Once a session is hijacked, the attacker can read private messages and deny service to the legitimate owner, potentially leading to data leakage and user disruptions.