The vulnerability is present in the verify_server function of the wx Endpoint in channel/wechatmp/common.py. When the wechatmp_token argument is omitted or left empty, the function fails to perform the necessary authentication check, allowing an unauthenticated request to be treated as valid. This flaw, which represents a CWE-287 authentication bypass and a CWE-306 missing authentication weakness, permits an attacker to invoke the /wx endpoint without providing a valid token, resulting in unauthorized access to the functionality that the endpoint exposes.

The issue affects installations of zhayujie chatgpt‑on‑wechat CowAgent version 2.1.0 and earlier that expose the /wx endpoint. Upgrading to version 2.1.1, or applying the patch identified by commit 3d7c68bac6ee74fad63f43cf99e45c62e202ed55, resolves the issue by enforcing a non‑empty wechatmp_token check and returning 403 Forbidden when the token is missing.

The CVSS score of 6.9 indicates moderate severity, while the EPSS score of <1% suggests the current exploitation likelihood is low. The vulnerability is not listed in the CISA KEV catalog. Based on the description, the exploit does not require privileged access or special code beyond sending a crafted HTTP request with an empty or omitted wechatmp_token. The likely attack vector is remote network access to the exposed /wx endpoint, as the attack may be initiated remotely. Anyone with network reach to the endpoint can send a simple HTTP request, making authentication bypass straightforward for any with access.