The vulnerability resides in the OAuth2 server component of AmoyLab Unla, which never authenticates the resource owner before generating an authorization code. As a result, a malicious actor can register a client, request a code through the /authorize endpoint, and exchange that code at /token to receive a functional access token. Possession of this token allows unrestricted access to all OAuth2‑protected services exposed by Unla, including any MCP prefixes, proxied upstream APIs, and injected credential endpoints, effectively granting the attacker the same privileges as a legitimate user.

AmoyLab Unla versions up to and including 0.10.0 contain this flaw. All deployments that have not applied a fix or updated the application to a later release are vulnerable.

The CVSS score of 8.8 categorizes this issue as high severity. Although EPSS data is unavailable and the vulnerability is not listed in KEV, the attack does not require privileged network access; it can be carried out by any host that can reach the /authorize and /token endpoints over HTTP. Consequently, the risk of exploitation remains significant for exposed instances.