The SUSE Security Team uses industry standard rating systems for security vulnerabilities.

Simplified rating

The simplified rating is used by various software companies to allow administrators a quick decision on whether to apply updates and at what schedule. We publish our Update Notices labeled with this rating.

Rating Definition
Critical This rating is given to flaws that could be easily exploited by a remote unauthenticated attacker and lead to system compromise (arbitrary code execution) without requiring user interaction. These are the types of vulnerabilities that can be exploited by worms. Flaws that require an authenticated remote user, a local user, or an unlikely configuration are not classed as critical impact.
Important This rating is given to flaws that can easily compromise the confidentiality, integrity, or availability of resources. These are the types of vulnerabilities that allow local users to gain privileges, allow unauthenticated remote users to view resources that should otherwise be protected by authentication, allow authenticated remote users to execute arbitrary code, or allow remote unauthenticated users to cause a denial of service without user interaction.
Moderate This rating is given to flaws that may be more difficult to exploit but could still lead to some compromise of the confidentiality, integrity, or availability of resources, under certain circumstances. These are the types of vulnerabilities that could have had a critical impact or important impact but are less easily exploited based on a technical evaluation of the flaw, or affect unlikely configurations. Local, persistent (service needs to be restarted) denial of service conditions for basic system services (kernel, systemd, polkit, dbus, ...) with and without user interaction should also be rated "moderate".
Low This rating is given to all other issues that have a security impact. These are the types of vulnerabilities that are believed to require unlikely circumstances to be able to be exploited, or where a successful exploit would give minimal consequences.

CVSS v2 Rating

Another common industry scoring system is the CVSS v2 base scoring, which converts the various vulnerability types, impacts and preconditions into a unified rating number.

SUSE is publishing CVSS v2 base scores for security issues that we are affected by besides the scores that are published by the National Vulnerability Database to our CVE pages.

CVSS v3 Rating

The common industry scoring system CVSS base scoring is being replaced by the CVSS v3 scoring system. It is very similar to the CVSS v2 version rating system, using slightly different ratings.

The final score result of both CVSS versions is between 0.0 and 10.0.

SUSE will start to publish CVSS v3 base scores in the first half of the year of 2017. CVSS v2 and v3 ratings will be supplied in parallel for a while, but v2 will be phased out in the future after a transition phase.