CVE-2026-73603 in Flowise
Summary
by MITRE • 08/13/2026
Flowise before 3.1.4 fails to validate chatflow visibility in the unauthenticated text-to-speech endpoint, allowing attackers to abuse private chatflow TTS credentials. Unauthenticated attackers can generate unlimited text-to-speech audio using stored OpenAI or ElevenLabs API keys by providing a valid chatflow UUID, incurring costs on the chatflow owner's account.
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Analysis
by VulDB Data Team • 08/13/2026
This vulnerability exists in Flowise versions prior to 3.1.4 where the text-to-speech endpoint lacks proper authentication and authorization checks for chatflow visibility. The flaw allows unauthenticated attackers to exploit private chatflow credentials by simply providing a valid chatflow uuid to generate unlimited audio content using stored API keys from OpenAI or ElevenLabs services. The technical implementation fails to verify whether the requesting entity has legitimate access rights to the specified chatflow, creating a critical authorization bypass that directly violates security principles outlined in cwe-285 and cwe-639. The vulnerability stems from insufficient input validation and access control mechanisms within the unauthenticated text-to-speech endpoint, which should require proper authentication tokens or session validation before processing requests. Attackers can leverage this weakness to consume API credits from the legitimate chatflow owner's account without any cost of ownership on their part, creating a significant financial risk that aligns with att&ck technique t1588.3 for resource hijacking and t1496 for resource exhaustion through unauthorized usage.
The operational impact of this vulnerability extends beyond simple financial loss as it enables attackers to consume substantial API credits from legitimate users who may not be aware their resources are being exploited. The attack vector requires minimal technical expertise since the attacker only needs to know a valid chatflow uuid, making this vulnerability particularly dangerous for widespread abuse. Organizations using Flowise for chatbot deployments face potential reputational damage when their API keys are misused, especially if they have premium accounts with limited credit allocations. The flaw creates a persistent threat where attackers can continuously generate audio content without detection, as the system does not implement rate limiting or usage monitoring for unauthorized access attempts. This situation directly violates principle of least privilege and demonstrates inadequate separation of concerns between public and private chatflow resources.
Mitigation strategies should include implementing robust authentication checks for all text-to-speech endpoints regardless of whether they are publicly accessible or private. The system must validate that the requesting entity has appropriate permissions to access the specified chatflow before processing any TTS requests. Additional protections should involve rate limiting mechanisms, API usage monitoring, and account activity logging to detect unauthorized consumption patterns. Organizations should also implement proper input sanitization and validation for all chatflow identifiers to prevent enumeration attacks that could lead to further exploitation. Security patches should enforce mandatory authentication tokens or session validation before allowing access to private chatflow resources, ensuring that only authorized users can leverage stored API credentials. The fix should align with security best practices defined in owasp top ten and nist cybersecurity framework, particularly focusing on access control and resource protection measures. Regular security audits should verify that no similar authorization bypass vulnerabilities exist in other endpoints that might expose sensitive data or resources to unauthorized access.