CVE-2026-56855

HIGH 7.5

Prevent DoS on deadlocked established channel in golang.org/x/crypto/ssh

CVSS Score

7.5

EPSS Score

0.0%

EPSS Percentile

0th

Previously, after a channel has been established, a malicious peer could send crafted messages that would deadlock the entire connection. Now, we handle all RFC 4254 channel messages; global requests are handled explicitly. Then, treat all other messages as a protocol error and tear the connection down instead of buffering and blocking.

Vendor	golang.org/x/crypto
Product	golang.org/x/crypto/ssh
Published	Sep 2, 2026
Last Updated	Sep 3, 2026

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Affected Versions

golang.org/x/crypto / golang.org/x/crypto/ssh

0 < 0.56.0

References

NVD ↗ CVE.org ↗ EPSS Data ↗

go.dev: https://go.dev/issue/81317 go.dev: https://go.dev/cl/826524 groups.google.com: https://groups.google.com/g/golang-announce/c/1y3fb2np35U pkg.go.dev: https://pkg.go.dev/vuln/GO-2026-6355

Credits

Will Mortensen