SSH "AllowedAuthentications" could allow an attacker to bypass the specified authentication mechanism
|ssh-allowedauthentications-bypass-auth (9163)||Medium Risk|
SSH (Secure Shell) could allow a remote attacker to bypass the specified authentication mechanism and gain unauthorized access to the server. If the "AllowedAuthentications" configuration option does not contain "Password" as an authentication option, a remote attacker could bypass the specified authentication mechanism and authenticate to the server using a weaker authentication mechanism.
Upgrade to the latest version of SSH (3.1.2 or later), available from the SSH Communications Web site. See References.
As a workaround, use "RequiredAuthentications" instead of "AllowedAuthentications".
- BugTraq Mailing List, Thu May 23 2002 - 12:22:29 CDT: [Fwd: Updated version of SSH Secure Shell available].
- CIAC Information Bulletin M-081: SSHD "AllowedAuthentications" Vulnerability.
- SSH Communications Security Web site: SSH - Products - SSH Secure Shell - Download.
- SSH Communications Security Web site: Security Advisory Regarding Vulnerability in SSH Secure Shell for Servers, SSH Secure Shell for Workstations (running in server mode) and SSH Secure Shell for Windows Servers versions 3.0 through 3.1.1.
- BID-4810: SSH Communications Secure Shell Server AllowedAuthentications Configuration Overriding Vulnerability
- CVE-2002-1646: SSH Secure Shell for Servers 3.0.0 to 3.1.1 allows remote attackers to override the AllowedAuthentications configuration and use less secure authentication schemes (e.g. password) than configured for the server.
- OSVDB ID: 18238: SSH Secure Shell for Servers AllowedAuthentications Remote Bypass
- US-CERT VU#341187: SSHD allows users to override AllowedAuthentications configuration thereby permitting users to provide any type of authentication
- SSH Secure Shell For Servers 3.0
- SSH Secure Shell For Servers 3.0.1
- SSH Secure Shell For Servers 3.1
- SSH Secure Shell For Servers 3.1.1
May 23, 2002
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