Yamux is a stream multiplexer over reliable, ordered connections such as TCP/IP. Prior to 0.13.10, the Rust implementation of Yamux can panic when processing a crafted inbound Data frame that sets SYN and uses a body length greater than DEFAULT_CREDIT (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. This vulnerability is fixed in 0.13.10.

Affected: crates.io: yamux

### 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 DEFAULT_CREDIT (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 = DEFAULT_CREDIT + 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

Affected: Ubuntu:25.10: rust-yamux, Ubuntu:26.04:LTS: rust-yamux

Yamux is a stream multiplexer over reliable, ordered connections such as TCP/IP. Prior to 0.13.10, the Rust implementation of Yamux can panic when processing a crafted inbound Data frame that sets SYN and uses a body length greater than DEFAULT_CREDIT (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. This vulnerability is fixed in 0.13.10.