A vulnerability exists in agentscope-ai AgentScope versions up to 2.0.11 that allows an attacker to manipulate the X-User-ID request header in the get_current_user_id function of the Agent Service. By providing a forged or arbitrary X-User-ID value, the service fails to perform proper authentication, effectively allowing an attacker to impersonate any user without credentials. This flaw results in an authentication bypass, granting unauthorized access to protected resources and functions exposed by the service.

Any deployment of agentscope-ai's AgentScope product with a version equal to or older than 2.0.11 is affected. The vulnerability is tied to the Agent Service component, specifically the get_current_user_id routine located in src/agentscope/app/deps.py. The affected vendor is agentscope-ai, and the product is AgentScope.

The CVSS base score for this flaw is 6.9, indicating a medium-to-high severity due to the impact of unauthorized access. The exploit is documented publicly and can be launched remotely by sending a request with a crafted X-User-ID header. Though the EPSS score is unavailable, the fact that the flaw has been disclosed and may already be in use suggests a realistic exploitation probability. The vulnerability is not listed in the CISA KEV catalog, but the lack of an official patch combined with the ability to perform authentication bypass means that environments running unpatched AgentScope are at significant risk.