Remote User Enumeration in OpenSSH by OpenSSH
CVE-2016-20012

5.3MEDIUM

Key Information:

Vendor
OpenBSD
Status
Openssh
Vendor
CVE Published:
15 September 2021

Summary

OpenSSH versions up to 8.7 contain a user enumeration vulnerability, allowing remote attackers to confirm if specific combinations of usernames and public keys are valid for a login session. This occurs because the server only sends a challenge when a particular combination may permit access. While this feature can potentially expose valid credentials, the vendor does not categorize this as a vulnerability, raising concerns about the overall security of SSH key authentication.

References

https://github.com/openssh/openssh-portable/pull/270
x_refsource_MISC
https://github.com/openssh/openssh-portable/blob/d0fffc88...
x_refsource_MISC
https://utcc.utoronto.ca/~cks/space/blog/tech/SSHKeysAreI...
x_refsource_MISC

EPSS Score

16% chance of being exploited in the next 30 days.

CVSS V3.1

Score:
5.3
Severity:
MEDIUM
Confidentiality:
Low
Integrity:
None
Availability:
Low
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

.