What’s Vulnerable › Vulnerabilities

CVE-2026-78662: Prevent DoS on deadlocked undecided channel in golang.org/x/crypto/ssh

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-09-02 · updated 2026-09-04
• Weakness: CWE-770

Description

Previously, a channel registered in the mux's chanList is not usable until it is established. A malicious peer was able flood the channel's incomingRequests, deadlocking the entire connection. Now, we add an atomic established state, set when a channel becomes usable. Until such a time, handlePacket drops every packet other than the open confirmation/failure, without blocking and without tearing down the connection.

Affected products

• golang.org/x/crypto/ssh: before 0.56.0 — fixed in 0.56.0
• Golang.Org/X/Crypto: before 0.56.0 — fixed in 0.56.0

How to fix

Upgrade to a fixed version: golang.org/x/crypto/ssh 0.56.0; Golang.Org/X/Crypto 0.56.0. Check the vendor advisory for mitigations.

References

• https://go.dev/cl/826504
• https://go.dev/issue/81316
• https://groups.google.com/g/golang-announce/c/1y3fb2np35U
• https://pkg.go.dev/vuln/GO-2026-6354

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