CVE-2026-31814: Protocol Yamux

High severity, CVSS 7.5. EPSS: 0.6% chance of exploitation in the next 30 days.

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.

Affected products

• Protocol Yamux: from 0.13.0, before 0.13.9 (fixed in 0.13.9)

Published 2026-03-13. Last modified 2026-06-17.