CVE-2026-90535

Flowise versions before 3.1.4 contain a missing-authorization flaw (CWE-862) in the /api/v1/text-to-speech/abort endpoint, which accepts user-supplied chatflowId and chatId values without verifying that the requester owns the session. An unauthenticated remote attacker who knows or guesses valid identifiers can submit abort requests that terminate other users' active chatflow predictions, causing targeted service disruption. The impact is limited to availability of individual chat sessions (CVSS 4.0: 6.3, medium) with no confidentiality or integrity impact. Anyone running a self-hosted Flowise instance on a version prior to 3.1.4, especially one exposed to untrusted networks, is affected. Exploitation status: a public advisory/PoC reference exists, EPSS is very low (0.2%, 16th percentile), and the flaw is not in the CISA KEV catalog, so no in-the-wild exploitation is known.

What to do: Upgrade Flowise to version 3.1.4 or later, where ownership verification for the abort endpoint is enforced. If immediate patching is not possible, place Flowise behind an authenticating reverse proxy or restrict network access so unauthenticated callers cannot reach /api/v1/text-to-speech/abort. Review application logs for abort requests referencing chatflowId/chatId values not associated with legitimate sessions as an indicator of abuse.