The vulnerability resides in the OpenApiRoute.chat_send handler of AstrBot Devs AstrBot and allows an attacker to alter the Username argument in an API request. This manipulation bypasses normal authentication, effectively granting the attacker the privileges of any specified user. The flaw maps to authentication failure (CWE‑287) and spoofing (CWE‑290) weaknesses and can lead to unauthorized bot operation, data leakage, or full control of the bot by a malicious actor.

AstrBot Devs AstrBot versions up to and including 4.25.5 are affected. The open_api chat_send route in astrbot/dashboard/routes/open_api.py is the entry point for the vulnerability. Any deployment of these releases that exposes the chat_send API is vulnerable until a patch is applied.

The exploit is remote, requiring only the ability to send crafted API requests to the chat_send endpoint; no privileged access is needed. The EPSS of less than 1% indicates that attacks are currently rare, and the CVSS score of 5.3 reflects moderate severity. The vulnerability is not listed in the CISA KEV catalogue, implying no documented widespread exploitation at this time. Nonetheless, because the flaw permits full authentication spoofing, the potential impact remains high if an attacker discovers or crafts a suitable request.