CVE-2021-36368

Name: CVE-2021-36368
Creator: NVD / NIST
Published: 2022-03-13T00:15:07.937+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

LOWCVSS 3.7/10EPSS 1.68%

Last modified Jun 17, 2026

CVE-2021-36368 is a low-severity vulnerability rated 3.7/10 on the CVSS scale. An issue was discovered in OpenSSH before 8.9. If a client is using public-key authentication with agent forwarding but without -oLogLevel=verbose, and an attacker has silently modified the server to support the None authentication option, then the user cannot determine whether FIDO authentication is going to confirm that the user wishes to connect to that server, or that the user wishes to allow that server to connect to a different server on the user's behalf. EPSS estimates a 1.68% chance of exploitation in the next 30 days.

Description

An issue was discovered in OpenSSH before 8.9. If a client is using public-key authentication with agent forwarding but without -oLogLevel=verbose, and an attacker has silently modified the server to support the None authentication option, then the user cannot determine whether FIDO authentication is going to confirm that the user wishes to connect to that server, or that the user wishes to allow that server to connect to a different server on the user's behalf. NOTE: the vendor's position is "this is not an authentication bypass, since nothing is being bypassed.

Metrics

CVSS 3.1

3.7/10

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

EPSS Probability

1.68%

73.9th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Openbsd	Openssh	< 8.9
Debian	Debian Linux	9.0
Debian	Debian Linux	10.0
Debian	Debian Linux	11.0

References

https://bugzilla.mindrot.org/show_bug.cgi?id=3316Issue Tracking, Third Party Advisory
https://docs.ssh-mitm.at/trivialauth.htmlThird Party Advisory
https://github.com/openssh/openssh-portable/pull/258Patch, Third Party Advisory
https://security-tracker.debian.org/tracker/CVE-2021-36368Third Party Advisory
https://www.openssh.com/security.htmlVendor Advisory
https://bugzilla.mindrot.org/show_bug.cgi?id=3316Issue Tracking, Third Party Advisory
https://docs.ssh-mitm.at/trivialauth.htmlThird Party Advisory
https://github.com/openssh/openssh-portable/pull/258Patch, Third Party Advisory
https://security-tracker.debian.org/tracker/CVE-2021-36368Third Party Advisory
https://www.openssh.com/security.htmlVendor Advisory

Timeline

Published: Mar 13, 2022
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-36368?

How severe is CVE-2021-36368?

CVE-2021-36368 has a CVSS score of 3.7/10 (LOW severity). The EPSS model estimates a 1.68% probability of exploitation in the next 30 days.

How do I fix CVE-2021-36368?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-36368?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST