CVE-2026-78662

The SSH connection multiplexer in golang.org/x/crypto registers a channel in its chanList before the channel is established, and a malicious SSH peer could flood that channel's incoming request queue with channel requests, deadlocking the entire SSH connection (CWE-770, allocation of resources without limits). An attacker who can act as an SSH peer — a client connecting to a Go-based SSH server, a server to which a Go SSH client connects, or a man-in-the-middle — triggers the flaw simply by sending the crafted request flood during channel setup. The result is denial of service: the affected connection hangs, and for server applications this can stall or exhaust connection handling. Any application built with the golang.org/x/crypto ssh package that communicates with untrusted SSH peers is affected; specific affected version ranges are not stated in the available data. No public proof-of-concept or known exploitation exists; EPSS puts the 30-day exploitation probability at about 0.3% (24th percentile), and the issue is not in CISA KEV.

What to do: Upgrade golang.org/x/crypto to a release containing the fix (the change adding an atomic established state so that, until a channel is established, all packets other than the open confirmation/failure are dropped without blocking or tearing down the connection), then rebuild and redeploy every Go binary that embeds the ssh package. Until patched, restrict SSH connectivity to trusted peers, since exploitation requires a malicious SSH endpoint; review Go vulnerability database announcements for the exact fixed version.