Flowise versions prior to 3.1.2 set the Access‑Control‑Allow‑Origin response header to the literal "*" on its text‑to‑speech (TTS) endpoint, regardless of the server’s CORS policy. This allows any website to send cross‑origin requests that trigger TTS generation using the target system’s stored credentials. The result is a drive‑by abuse that lets an attacker execute server‑side API calls with a victim’s privileges, compromising confidentiality and integrity of any data accessed by the TTS service.

The affected product is Flowise, a conversational AI platform. Versions before 3.1.2 are impacted; the vulnerability is present in the Flowise 3.x series that has not applied the 3.1.2 patch. Operators using Flowise should verify that they are not running a vulnerable version and that the server is not exposed to untrusted origins.

The CVSS score of 6.9 reflects a medium severity due to the requirement for a cross‑origin browser request and the use of stored credentials. The EPSS score is not available, and the vulnerability is not listed in the CISA KEV catalog, indicating no current widespread exploitation is reported. Attackers can exploit this by hosting a malicious web page that sends a request to the TTS endpoint from a client’s browser; the hardcoded wildcard bypasses the default CORS restrictions, enabling the request to succeed and the server to process it using the victim’s identities.