OpenSSH - User Enumeration via Covert Timing Channel
Summary
DLA-578-1: openssh - security update. Affects openssh versions < 1:6.0p1-4+deb7u5. Fixed in 1:6.0p1-4+deb7u5. How to fix ↓
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Background
OpenSSH is a secure shell (SSH) client and server that provides secure remote access to systems and encrypted communication between systems. It is widely used for secure remote administration and file transfer. The OpenSSH package in Debian 7 Wheezy is affected by a user enumeration vulnerability.
Vulnerability Detail
The vulnerability, identified as CVE-2016-6210, allows an attacker to enumerate valid usernames on a target system by exploiting a covert timing channel. By measuring the time it takes for the server to respond to authentication requests, an attacker can determine if a username is valid or not. This information can be used to launch further attacks, such as brute-forcing passwords for valid usernames.
How To Fix
Minimum fixed version
1:6.0p1-4+deb7u5
This is the first release that contains the fix.
sudo apt-get install --only-upgrade opensshTip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
There is no specific workaround mentioned for this vulnerability.
Conclusion
The OpenSSH package in Debian 7 Wheezy is affected by a user enumeration vulnerability that can be exploited through a covert timing channel. Upgrading to the recommended version of openssh will mitigate this vulnerability. For further support on vulnerability remediation, contact DevNack.com.
See every vulnerability recorded for openssh →
FAQ
OpenSSH is a secure shell (SSH) client and server that provides secure remote access to systems and encrypted communication between systems.
User enumeration is the process of determining valid usernames on a target system. In this vulnerability, an attacker can use a covert timing channel to determine if a username is valid or not.
A covert timing channel is a method of communication between two entities that is hidden within the timing of certain events. In this vulnerability, the timing of server responses to authentication requests is used to determine the validity of usernames.
The user enumeration vulnerability in OpenSSH can be used by attackers to gather information about valid usernames on a target system. This information can then be used to launch further attacks, such as brute-forcing passwords for valid usernames.
To fix this vulnerability, it is recommended to upgrade the openssh package to version 6.0p1-4+deb7u5 or later. Follow the instructions provided by Debian LTS for applying updates to your system.
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