CVE-2026-56855

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

HIGH
7.5
CVSS Score
Published: September 2, 2026 at 07:37 PM UTC
Updated: September 4, 2026 at 04:46 PM UTC
2 products affected across 2 vendorsCryptoSSH

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Severity
HIGH7.5
Exploit prediction
EPSS 0.5%
SSVC
No known exploit

Description

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

v < 0.56.0
Affected range stops below 0.56.0, so it looks safe — our inference, not a vendor statement
v < 0.56.0
Affected range stops below 0.56.0, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

References (4)

Issue TrackingVendor Advisory
Source: cverecord
https://go.dev/issue/81317
Patch
Source: cverecord
https://go.dev/cl/826524
Mailing ListVendor Advisory
Source: cverecord
https://groups.google.com/g/golang-announce/c/1y3fb2np35U
Vendor Advisory
Source: cverecord
https://pkg.go.dev/vuln/GO-2026-6355

SSVC — Action Prioritization

SSVCNo known exploitAutomatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

7.5HIGHCISA-ADP
Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
NONE
Availability
HIGH
Vector?

Quick Info

StatusANALYZED
CWE
CWE-770

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