The /api/v1/oauth2-credential/refresh/:credentialId endpoint in Flowise was included in the whitelist of URLs and could be accessed without authentication. By sending a POST request to this endpoint, an attacker can cause the application to decrypt a stored OAuth credential, send a refresh request to the provider, and receive a newly minted access token in the response body. The attacker only needs the credential ID to obtain the token, which can then be used to access the victim’s connected third‑party services and to exhaust the provider’s refresh‑token quota. This flaw is a confidentiality violation, classified as CWE‑200.

The vulnerability affects Flowise by FlowiseAI versions prior to 3.1.3. All releases up to and including 3.1.2 are susceptible. The issue is fixed in version 3.1.3.

The CVSS score of 9.2 indicates a high‑severity weakness. The EPSS score is not reported, so exploitation probability is unknown, and the vulnerability is not listed in the CISA KEV catalog. A remote attacker must know a valid credential ID to trigger the flaw; with that information the attacker can access protected services and potentially drain refresh‑token allowances. The lack of authentication on a public endpoint makes attack feasible from any network without additional access.