CVE-2021-36368
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…
Does this matter?
Lower severity and a low EPSS score (1.68%). Track it; it rarely justifies an emergency change on its own.
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.
- CVSS 3.1
- 3.7 LOWCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
- EPSS
- 1.68% probability · 76th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-287
- Affected
- openbsd/openssh · debian/debian linux
- Source
- cve@mitre.org
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
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.