CVE-2018-15473 is a medium-severity vulnerability affecting OpenSSH versions up to and including 7.7. This vulnerability allows user enumeration due to the system not delaying bailout for an invalid authenticating user until after the packet containing the request has been fully parsed. As a result, a remote attacker can test whether a certain user exists on a target OpenSSH server.

How do I know if I'm affected?

If you're using OpenSSH up to version 7.7, Debian Linux 8.0 and 9.0, Red Hat Enterprise Linux Desktop 6.0 and 7.0, Red Hat Enterprise Linux Server 6.0 and 7.0, Red Hat Enterprise Linux Workstation 6.0 and 7.0, or Canonical Ubuntu Linux 14.04, 16.04, and 18.04, you might be affected by the vulnerability. This vulnerability allows user enumeration, meaning a remote attacker can check if a certain user exists on your OpenSSH server. To know if you're affected, check your system's OpenSSH version and the operating system version.

What should I do if I'm affected?

If you're affected by the vulnerability, it's important to update your system to mitigate the risk. First, check for available updates for your specific operating system. For example, Red Hat Enterprise Linux users can follow the RHSA-2019:0711 Security Advisory instructions. Ubuntu users can refer to the USN-3809-1 OpenSSH Vulnerabilities Notice for update details. Always keep your system up-to-date to ensure security.

Is this in CISA’s Known Exploited Vulnerabilities Catalog?

The CVE-2018-15473 vulnerability is not listed in CISA's Known Exploited Vulnerabilities Catalog. This vulnerability, also known as OpenSSH user enumeration, allows a remote attacker to test if a specific user exists on a target OpenSSH server. It affects OpenSSH versions up to 7.7 and various operating systems. To mitigate the risk, users should update their systems and follow the provided advisories and solutions.

Weakness enumeration

The weakness enumeration for this vulnerability is categorized as CWE-362, a "Race Condition" weakness, which occurs when concurrent execution uses shared resources without proper synchronization. This vulnerability affects OpenSSH up to version 7.7.

For more details

CVE-2018-15473, a medium-severity vulnerability affecting OpenSSH versions up to 7.7, allows user enumeration due to improper handling of invalid authenticating users. This vulnerability impacts various systems, including Debian Linux, Red Hat Enterprise Linux, and Canonical Ubuntu Linux. To ensure security, users should update their systems and follow the provided advisories and solutions. For a comprehensive understanding of the vulnerability, including its description, severity, technical details, and known affected software configurations, visit the NVD page or the links below.

• oss-security - OpenSSH Username Enumeration

• RHSA-2019:0711 - Security Advisory

• Security Advisory

• USN-3809-1: OpenSSH vulnerabilities | Ubuntu security notices | Ubuntu