CVE-2021-36368Network attack vector

FIDO confirmation ambiguity via silent None authentication

Published Mar 12, 2022 · Updated May 29, 2026

Authentication ambiguity in the OpenSSH client before 8.9 allows remote attackers to obscure what a FIDO confirmation authorizes. The client presents the same FIDO confirmation when authenticating to a modified server that accepts None authentication and when its forwarded agent signs a connection from that server to another host. Reachability requires public-key authentication, agent forwarding, a FIDO key, and non-verbose logging; OpenSSH disputes that this behavior constitutes an authentication bypass.

CVSS severity3.7
Low
EPSS probability1.68%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Authentication ambiguity in the OpenSSH client before 8.9 allows remote attackers to obscure what a FIDO confirmation authorizes. The client presents the same FIDO confirmation when authenticating to a modified server that accepts None authentication and when its forwarded agent signs a connection from that server to another host. Reachability requires public-key authentication, agent forwarding, a FIDO key, and non-verbose logging; OpenSSH disputes that this behavior constitutes an authentication bypass.

The record

CVE
CVE-2021-36368
Published
Mar 12, 2022
Updated
May 29, 2026
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-287
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 12, 2022CVE publishedPublication date reported by the CVE source.
  2. May 29, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

3.7NVDCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-287Improper Authentication

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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