The remote host seems to be running an SSH server that could allow an attacker to determine the existence of a given login by comparing the time the remote sshd daemon takes to refuse a bad password for a nonexistent login compared to the time it takes to refuse a bad password for a valid login.

An attacker could use this flaw to set up a brute-force attack against the remote host.

The version of SunSSH running on the remote host has an information disclosure vulnerability.  A design flaw in the SSH specification could allow a man-in-the-middle attacker to recover up to 32 bits of plaintext from an SSH-protected connection in the standard configuration.  An attacker could exploit this to gain access to sensitive information.

Note that this version of SunSSH is also prone to several additional issues but Nessus did not test for them.

Updated OpenSSH packages are now available. These updates close an information leak caused by sshd's interaction with the PAM system.

OpenSSH is a suite of network connectivity tools that can be used to establish encrypted connections between systems on a network and can provide interactive login sessions and port forwarding, among other functions.

When configured to allow password-based or challenge-response authentication, sshd (the OpenSSH server) uses PAM (Pluggable Authentication Modules) to verify the user's password. Under certain conditions, OpenSSH versions prior to 3.6.1p1 reject an invalid authentication attempt without first attempting authentication using PAM.

If PAM is configured with its default failure delay, the amount of time sshd takes to reject an invalid authentication request varies widely enough that the timing variations could be used to deduce whether or not an account with a specified name existed on the server.
This information could then be used to narrow the focus of an attack against some other system component.

These updates contain backported fixes that cause sshd to always attempt PAM authentication when performing password and challenge-response authentication for clients.

The remote host is using a version of Portable OpenSSH that may allow an attacker to determine if an account exists or not by a timing analysis. 

sshd in OpenSSH 3.6.1p2 and earlier, when PermitRootLogin is disabled and using PAM keyboard-interactive authentication, does not insert a delay after a root login attempt with the correct password, which makes it easier for remote attackers to use timing differences to determine if the password step of a multi-step authentication is successful, a different vulnerability than CVE-2003-0190.

This plugin only works with Tenable.ot.
Please visit https://www.tenable.com/products/tenable-ot for more information.

ID	Name	Product	Family	Published	Updated	Severity
11574	OpenSSH w/ PAM Multiple Timing Attack Weaknesses	Nessus	Misc.	5/6/2003	4/11/2022	critical
55992	SunSSH < 1.1.1 / 1.3 CBC Plaintext Disclosure	Nessus	Misc.	8/29/2011	9/21/2020	critical
12407	RHEL 2.1 : openssh (RHSA-2003:224)	Nessus	Red Hat Local Security Checks	7/6/2004	1/14/2021	high
1984	Portable OpenSSH < 3.6.1p2 PAM Timing Side-Channel Weakness	Nessus Network Monitor	SSH	8/20/2004	3/6/2019	medium
503056	Siemens SCALANCE X-200RNA Switch Devices Concurrent Execution Using Shared Resource with Improper Synchronization (CVE-2003-1562)	Tenable OT Security	Tenable.ot	3/13/2025	3/14/2025	high

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