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 (DEFAULTCREDIT). 2. Send a WindowUpdate on that stream with a very large credit value (e.g. 0xFFFF0000) 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
Summary The Rust implementation of Yamux can panic when processing a crafted inbound Data frame that sets SYN and uses a body length greater than DEFAULTCREDIT (e.g. 262145). On the first packet of a new inbound stream, stream state is created and a receiver is queued before oversized-body validation completes. When validation fails, the temporary stream is dropped and cleanup may call remove(...).expect("stream not found"), triggering a panic in the connection state machine. This is remotely reachable over a normal Yamux session and does not require authentication. kind of vulnerability is it? Who is Attack Scenario An attacker that can establish a Yamux session with a target node can crash the target by sending a single validly encoded Yamux Data|SYN frame with an oversized body: 1. Establish a standard authenticated transport session that negotiates Yamux. 2. Send one Yamux frame with: - Tag = Data - Flags = SYN - StreamId = 1 (or any new inbound stream id) - Length = DEFAULTCREDIT + 1 (e.g. 262145) - Body of matching size This can trigger a panic (stream not found) and terminate the process, depending on host application panic policy. Patches Users should upgrade to yamux v0.13.10
This vulnerability was originally submitted by @revofusion to the Ethereum Foundation bug bounty program