CVE-2026-39889: PraisonAI: unauth A2U stream leaks all agent activity

The A2U (Agent-to-User) event stream server in PraisonAI exposes all agent activity without authentication. This is a separate component from the gateway server fixed in CVE-2026-34952. The create_a2u_routes() function registers the following endpoints with NO authentication checks: - GET /a2u/info — exposes server info and stream names - POST /a2u/subscribe — creates event stream subscription - GET /a2u/events/{stream_name} — streams ALL agent events - GET /a2u/events/sub/{id} — streams events for subscription - GET /a2u/health — health check An unauthenticated attacker can: 1. POST /a2u/subscribe → receive subscription_id 2. GET /a2u/events/sub/{subscription_id} → receive live SSE stream of all agent events including responses, tool calls, and thinking This exposes sensitive agent activity including responses, internal reasoning, and tool call arguments to any network attacker. <img width="1512" height="947" alt="image" src="https://github.com/user-attachments/assets/3438f3ea-75ec-4978-9dd9-d9a6da42c248" /> <img width="1512" height="571" alt="image" src="https://github.com/user-attachments/assets/ee3313f6-f522-48f7-9c06-e5e265c6aeb4" /> [1] POST /a2u/subscribe (no auth token) Status: 200 Response: {"subscription_id":"sub-a1ad8a6edd8b","stream_name":"events", "stream_url":"http://testserver/a2u/events/sub-a1ad8a6edd8b"} Got subscription_id: sub-a1ad8a6edd8b [2] GET /a2u/info (no auth token) Status: 200 Response: {"name":"A2U Event Stream","version":"1.0.0", "streams":["events"],"event_types":["agent.started","agent.thinking", "agent.tool_call","agent.response","agent.completed","agent.error"]} [3] GET /a2u/health (no auth token) Status: 200 Response: {"status":"healthy","active_subscriptions":1,"active_streams":1} Impact: Attacker can subscribe and receive ALL agent events including responses, tool calls, and internal reasoning in real-time

An attacker targeting an organization using PraisonAI enumerates the A2U component via /a2u/health fingerprinting or path discovery. With no credentials, they POST to /a2u/subscribe and receive a subscription_id in the response. They then open a persistent SSE connection to GET /a2u/events/sub/{subscription_id} and begin receiving a continuous real-time stream of all agent events: 'agent.thinking' events expose internal reasoning chains and potential system prompt fragments; 'agent.tool_call' events reveal tool invocations with full argument payloads including any database queries, API calls, file read operations, or credentials passed to tools; 'agent.response' events deliver the agent's final outputs. The attacker gains complete operational visibility into the AI agent's activity with zero interaction from the victim and no risk of detection beyond standard HTTP access logs.