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Hi everyone:</div>
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</div>
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I found a heap-use-after-free in the LIVE555 RTSP server when an</div>
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OnDemandServerMediaSubsession uses reuseFirstSource=True.</div>
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</div>
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Tested version: LIVE555 2026.06.29</div>
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</div>
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Summary:</div>
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Two clients can SETUP the same stream/track, sharing one StreamState. If both</div>
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then send a failed re-SETUP for the same track/session, the shared StreamState</div>
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reference count can become inconsistent. Later full server cleanup crashes with</div>
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a UAF.</div>
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</div>
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Client request shape:</div>
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Each of two separate RTSP client connections first sends normal requests like:</div>
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DESCRIBE rtsp://<server>/live RTSP/1.0</div>
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CSeq: 1</div>
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Accept: application/sdp</div>
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</div>
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SETUP rtsp://<server>/live/track1 RTSP/1.0</div>
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CSeq: 2</div>
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Transport: RTP/AVP;unicast;client_port=<rtp>-<rtcp></div>
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PLAY rtsp://<server>/live RTSP/1.0</div>
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CSeq: 3</div>
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Session: <session-id></div>
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Range: npt=0-</div>
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</div>
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Then each client sends a second SETUP for the same track/session, but without</div>
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the Transport header:</div>
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SETUP rtsp://<server>/live/track1 RTSP/1.0</div>
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CSeq: 4</div>
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Session: <session-id></div>
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<br>
</div>
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Both malformed re-SETUP requests return "461 Unsupported Transport". The client</div>
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connections remain open until the server performs full cleanup.</div>
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</div>
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Root cause:</div>
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RTSPClientSession::handleCmd_SETUP_afterLookup2() deletes the old stream token</div>
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before fully validating the new SETUP request. If the new SETUP fails, the</div>
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shared StreamState reference count has already been decremented, while another</div>
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session may still hold a stale streamToken.</div>
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ASan stack:</div>
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OnDemandServerMediaSubsession::deleteStream()</div>
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liveMedia/OnDemandServerMediaSubsession.cpp:383</div>
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RTSPClientSession::reclaimStreamStates()</div>
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liveMedia/RTSPServer.cpp:1307</div>
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GenericMediaServer::cleanup()</div>
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I have a working PoC/reproducer ready. Because this is a remotely triggerable</div>
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UAF and the live-devel list is public, I would prefer not to post the full PoC</div>
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publicly. I can share it privately with the maintainer if needed.</div>
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If you confirm this bug and decide to request a CVE for this issue,</div>
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I can provide any additional technical details or materials you need.</div>
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Best regards,</div>
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Zhou Qingyang</div>
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