CVE-2026-31814: Yamux 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 (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
Other sources
Yamux is a stream multiplexer over reliable, ordered connections such as TCP/IP. From 0.13.0 to before 0.13.9, 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. This vulnerability is fixed in 0.13.9.
— MITRE
Affected Software
Event History
Frequently Asked Questions
What is the severity of CVE-2026-31814?
CVE-2026-31814 is considered a critical vulnerability due to the potential for arithmetic overflow affecting send-window accounting.
How do I fix CVE-2026-31814?
To mitigate CVE-2026-31814, upgrade to yamux version 0.13.9 or later, where the vulnerability has been addressed.
What types of applications are affected by CVE-2026-31814?
CVE-2026-31814 affects applications utilizing the Rust implementation of the Yamux protocol within the specified version range.
What could happen if CVE-2026-31814 is exploited?
Exploitation of CVE-2026-31814 could lead to unexpected behavior or a denial of service due to the overflow in send-window accounting.
How can I determine if I am using a vulnerable version related to CVE-2026-31814?
Check the version of the yamux package in your application; versions between 0.13.0 and 0.13.9 are vulnerable to CVE-2026-31814.