CVE-2021-36368

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.

• CWE-287
• CWE-287

• 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

Published

Mar 13, 2022

Last Modified

Jun 17, 2026

Status

Modified

• How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
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