CVE-1999-1231
MediumExploitation Probability (EPSS)
Elevated risk70th percentile - higher than 70% of all known CVEs
Summary
ssh version 2.0.12, and possibly other versions, allows valid usernames to attempt to enter the correct password multiple times, but only prompts for a password once for an invalid username. This allows remote attackers to determine user account names on the server.
Risk Assessment
Attackers can identify existing user accounts, increasing the risk of further attacks such as password guessing attempts.
Recommendation
It is recommended to update the ssh software to the latest version to minimize the risk associated with username disclosure.
Other vulnerabilities in ssh
See all- CVE-2026-56854High
The source-address critical option in the Permissions returned by an authentication callback was only enforced for the PublicKeyCallback and VerifiedPublicKeyCallback paths, extending the fix for CVE-2026-46595. Permissions returned by the PasswordCallback, KeyboardInteractiveCallback, NoClientAuthCallback, and GSSAPIWithMICConfig.AllowLogin callbacks were not validated against the client's remote address, so a source-address restriction set by those callbacks was silently ignored. The check is now applied to the Permissions returned by any authentication callback.
- CVE-2026-39828Medium
In SSH, when an authentication callback returned PartialSuccessError with non-nil Permissions, those permissions were silently discarded. This could drop certificate restrictions like force-command after a second factor. Returning non-nil Permissions with PartialSuccessError now results in a connection error.
- CVE-2000-0217Medium
The default configuration of SSH allows X forwarding, which could allow a remote attacker to control a client's X sessions via a malicious xauth program.
- CVE-1999-1159Medium
SSH version 2.0.11 and earlier allows local users to request remote forwarding from privileged ports without being root.
Original NVD description (English source)
ssh 2.0.12, and possibly other versions, allows valid user names to attempt to enter the correct password multiple times, but only prompts an invalid user name for a password once, which allows remote attackers to determine user account names on the server.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS