Flowise is vulnerable to an authentication bypass that allows an attacker without credentials to retrieve OAuth 2.0 access tokens from a public chatflow configuration. By accessing the exposed endpoint, an attacker can obtain internal token identifiers and use them to refresh and generate valid access tokens, potentially enabling unauthorized access to downstream services and sensitive data. The weakness is an instance of improper authorization, classified as CWE-306.

The vulnerability affects all Flowise instances deployed by FlowiseAI prior to version 3.1.0, including all releases of the Flowise platform before that point.

With a CVSS score of 7.7, the flaw presents a moderate to high risk level. The EPSS score of less than 1% suggests that, historically, exploitation attempts are infrequent, and the vulnerability is not currently catalogued in the CISA KEV list. The likely attack vector is remote, unauthenticated, through the public chatflow configuration endpoint, as inferred from the description. Given the disclosed capability to obtain usable tokens, the potential impact on confidentiality and integrity is significant if an attacker can leverage the tokens to impersonate legitimate users.