CVE-2026-73568: py-libp2p: yamux connection DoS via oversized data frame

py-libp2p is the Python implementation of the libp2p networking stack. In 0.7.0 and earlier, the yamux handleincoming() method in libp2p/streammuxer/yamux/yamux.py reads an attacker-controlled 32-bit DATA frame length with readexactly() before validating it against MAXWINDOWSIZE or checking whether streamid exists. A peer that completes the standard Noise handshake can send a 12-byte frame declaring a 0xFFFFFFFF body and then withhold the body, causing the sequential yamux read loop used by the default newhost() configuration to block and preventing every stream on that connection from making progress. No fixed version is available as of this review.