A timing-related security flaw, called a race condition, has been found in Red Hat's libuser software, a component commonly used on Red Hat-based server systems.
This flaw can be exploited by people who already have authorized access to your server to corrupt the system's core user account file, /etc/passwd. If this file is damaged, it can cause your server or website to crash and become unavailable without warning. It may also let an attacker gain higher access privileges than they are permitted, which could allow them to make unauthorized changes to your site or access private data stored on your server.
Source: CISA Known Exploited Vulnerabilities Catalog — https://nvd.nist.gov/vuln/detail/CVE-2015-3246
