Attack Chain

1. An unauthenticated remote attacker identifies an exposed pipecat development runner with an accessible /ws WebSocket endpoint, typically fronted by a public proxy.
2. The attacker establishes an unauthenticated WebSocket connection to the /ws endpoint on the pipecat runner.
3. The attacker sends a crafted Twilio WebSocket "start" handshake message, embedding an attacker-controlled callSid (e.g., CAATTACKER1337INJECTED00000000001) into the JSON payload.
4. The pipecat runner, lacking authentication checks, accepts the connection and extracts the attacker-supplied callSid from the handshake message without validation.
5. When the pipecat pipeline terminates (e.g., via an EndFrame or CancelFrame), its TwilioFrameSerializer (which defaults auto_hang_up to True) automatically triggers the _hang_up_call() function.
6. The _hang_up_call() function constructs a Twilio REST API URL, incorporating the attacker-supplied callSid into the endpoint (e.g., api.twilio.com/.../Calls/{attacker_call_sid}.json).
7. The pipecat runner then uses its own configured TWILIO_ACCOUNT_SID and TWILIO_AUTH_TOKEN (from environment variables) to send an authenticated POST request to the constructed Twilio API URL.
8. This POST request forcibly terminates the call associated with the attacker-supplied callSid, leading to denial of service or abuse of the operator's telephony account.

Impact

This vulnerability, categorized as Missing Authorization (CWE-862), allows an unauthenticated network attacker to remotely interact with an exposed pipecat development runner. If the runner is configured with live Twilio, Telnyx, or Plivo credentials, the attacker can forcibly terminate active calls by injecting a known or guessed callSid into the WebSocket handshake. This leads to denial of service for ongoing communications and enables the attacker to abuse the organization's telephony provider credentials for unauthorized call-control actions. Organizations relying on pipecat for telephony integrations that have inadvertently exposed development instances to the public internet are at risk of significant operational disruption and potential compromise of their telephony accounts.

Recommendation

• Review pipecat runner deployments: Ensure pipecat development runners are strictly bound to localhost or internal, trusted network interfaces, and are not accessible from untrusted networks, as highlighted in the Overview.
• Network Monitoring and Blocking: Monitor outbound connections from pipecat runner hosts to telephony API endpoints such as api.twilio.com, api.telnyx.com, and api.plivo.com (listed in IOCs), and implement network filtering or segmentation to restrict such traffic unless explicitly required and carefully configured.
• Detection Engineering: Deploy the Sigma rule "Pipecat Telephony Runner Outbound Call Control Request" from this brief to your SIEM and tune it to identify anomalous outbound call termination requests originating from pipecat processes.