Librechat CVE-2026-31949

CVSS 6.5 (Medium-High) reflects AV:Network, AC:Low, PR:Legitimate (authenticated), UI:None, S:Unchanged, C:None, I:None, A:High—indicating easy remote exploitation by any authenticated user with no special conditions. The attack complexity is trivial (malformed JSON in request body), but the impact is severe: complete application unavailability. However, real-world risk is moderated by two factors: (1) Attack requires authentication, reducing the attacker pool to legitimate users or those with compromised credentials, and (2) No KEV status, active exploitation reports, or public POC evidence suggests this remains largely theoretical or exploited only in targeted scenarios. The vulnerability is automatable and has high technical impact (service-level DoS), but the authentication barrier and apparent lack of weaponization lower urgency compared to unauthenticated DoS. SSVC framework would classify this as moderate priority: exploitation is straightforward but requires authenticated access; impact is high (service unavailable) but not data-compromising.

An authenticated user (either legitimate with malicious intent or an attacker with compromised credentials) sends a DELETE request to https://target-librechat-instance/api/convos with a malformed JSON body such as {} or {"other_field": "value"}, intentionally omitting the 'arg' field. The route handler attempts destructuring like const { arg } = req.body without checking if arg exists. JavaScript throws TypeError: Cannot destructure property 'arg' of 'undefined' or similar. This exception is not caught by the route handler's try-catch block (if absent) or Express error middleware (bypassed), triggering an unhandled exception that Node.js escalates to process.exit(1). The entire LibreChat application crashes, disconnecting all users and making the service unavailable until manually restarted. An attacker could repeat this attack every time the service recovers, creating a sustained DoS condition. No known public POC code has been released, though exploitation is trivial given the low technical barrier (HTTP POST with malformed JSON).