Yamux vulnerable to remote Panic via malformed WindowUpdate credit

Sumary

The Rust implementation of Yamux accepts WindowUpdate credit values from the remote peer and applies them to per-stream send-window state.
A specially crafted WindowUpdate can cause arithmetic overflow in send-window accounting, which triggers a panic in the connection state machine. This is remotely reachable over a normal network connection and does not require authentication.

Attack Scenario

An attacker that can establish a Yamux session with a target node can crash the target by sending two validly encoded Yamux frames:

1. Open a stream (e.g. DATA + SYN) so the stream exists with initial send-window state (DEFAULT_CREDIT).
2. Send a WindowUpdate on that stream with a very large credit value (e.g. 0xFFFF_0000) such that adding credit to the current send-window overflows u32.

Impact

Remote unauthenticated denial of service.
An attacker can repeatedly trigger panics by reconnecting and replaying the crafted frame sequence.

Patches

Users should upgrade to yamux v0.13.9

This vulnerability was originally submitted by @revofusion to the Ethereum Foundation bug bounty program