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

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-56855
StatePUBLISHED
AssignerGo
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-02 20:17:36 UTC
Updated2026-09-04 16:34:56 UTC
DescriptionPreviously, 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.

Risk And Classification

Primary CVSS: v3.1 7.5 HIGH from ADP

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS: 0.003780000 probability, percentile 0.309750000 (date 2026-09-07)

Problem Types: CWE-770 | CWE-770: Allocation of Resources Without Limits or Throttling | CWE-770 CWE-770 Allocation of Resources Without Limits or Throttling

VersionSourceTypeScoreSeverityVector
3.1ADPDECLARED7.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
3.1134c704f-9b21-4f2e-91b3-4a467353bcc0Secondary7.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Application Golang Crypto All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Golang.orgxcrypto Golang.org/x/crypto/ssh affected 0.56.0 semver Not specified

References

ReferenceSourceLinkTags
groups.google.com/g/golang-announce/c/1y3fb2np35U [email protected] groups.google.com Mailing List, Vendor Advisory
go.dev/issue/81317 [email protected] go.dev Issue Tracking, Vendor Advisory
go.dev/cl/826524 [email protected] go.dev Patch
pkg.go.dev/vuln/GO-2026-6355 [email protected] pkg.go.dev Vendor Advisory
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: Will Mortensen (en)

© CVE.report 2026

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