Flowise: Unauthenticated TTS endpoint accepts arbitrary credential IDs — enables API credit abuse via stored credentials — flowise
Authorization Bypass Through User-Controlled KeySummary
The text-to-speech generation endpoint (POST /api/v1/text-to-speech/generate) is whitelisted (no auth) and accepts a credentialId directly in the request body. When called without a chatflowId, the endpoint uses the provided credentialId to decrypt the stored credential (e.g., OpenAI or ElevenLabs API key) and generate speech.
Root Cause
// packages/server/src/controllers/text-to-speech/index.ts:58-64
} else {
// Use TTS config from request body
provider = bodyProvider
credentialId = bodyCredentialId // ← attacker-controlled credential ID
voice = bodyVoice
model = bodyModel
}
Docker Validation
POST /api/v1/text-to-speech/generate with arbitrary credentialId in body: endpoint processes request, sends SSE tts_start event, only fails when credential doesn't exist — proves code path runs without authentication.
Impact
- Use victim's API keys (OpenAI, ElevenLabs, Azure, Google) without authorization
- Burn API credits on the victim's account
- Generate unlimited speech content at victim's expense
- Combined with credential ID leak from Finding 2, this is trivially exploitable
Suggested Fix
Remove the TTS endpoint from WHITELIST_URLS or validate that the credential belongs to the chatflow being used:
// Only allow credentialId when it matches the chatflow's TTS configuration
if (!chatflowId) {
return res.status(401).json({ message: 'Authentication required' })
}
References
packages/server/src/controllers/text-to-speech/index.tslines 10-162packages/server/src/utils/constants.tsline 41 (whitelist entry)
Credits
- Shinobi Security - https://github.com/shinobisecurity
| Software | From | Fixed in |
|---|---|---|
flowise
|
- | 3.1.0 |
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