The vulnerability is an Insecure Direct Object Reference in LibreChat's SSE streaming endpoint, permitting an authenticated user who knows or guesses a stream identifier to receive real‑time chat data belonging to another user. This leak can reveal private messages, AI responses, and tool usage, thereby compromising confidentiality. The weakness corresponds to CWE‑284 (Improper Access Control) and CWE‑639 (Privilege Dropping).

The affected product is LibreChat by Danny Avila, specifically the release candidates version 0.8.2‑rc2 and 0.8.2‑rc3. The issue is resolved in the stable 0.8.2 release. No other vendors or products are listed as affected.

The CVSS v3.1 base score is 5.3, indicating moderate severity. The EPSS score is less than 1%, suggesting a low probability of exploitation. The vulnerability is not present in CISA’s KEV catalog. An attacker must be authenticated and must determine a valid stream ID; the missing ownership check allows subscription to any stream ID, which is the likely attack vector for insider or compromised account scenarios.