Oracle CVSS: ‘Partial+’ is ‘Useful-’By Adrian Lane
Oracle announced the April 2011 CPU this week, with just a few moderate security issues for the database. Most DBAs monitor Oracle’s Critical Patch Updates (CPU) and are already familiar with the Common Vulnerability Scoring System (CVSS). For those of you who are not, it’s a method of calculating the relative risk of software and hardware vulnerabilities, resulting in a score that describes the potential severity of the vulnerability if an attacker were to exploit the problem. The scores are provided to help IT and operations teams decide what to patch and when. Vendors are cagey about providing vulnerability information – under the belief that any information helps attackers create exploits – so CVSS is a compromise to help customers without overly helping adversaries.
Oracle uses CVSS scoring to categorize vulnerabilities, and publishes the scores with the quarterly release of their CPUs. When Oracle database vulnerabilities are found, they provide the raw data fed into the scoring system to generate the score included with the patch announcement.
Most of the DBA community is not happy with the CVSS system, as it provides too little information to make informed decisions. The scoring methodology of assembling ‘base metrics’ with time and environmental variables is regarded as fuzzy logic, intended to obfuscate the truth more than to help DBAs understand risk. The general consensus is that risk scores have low value, but anything with a high score warrants further investigation. Google and 3rd party researchers become catalysts for patching decisions. Still, it’s better than nothing, and most DBAs are simply too busy to make much fuss about it, so there is little more that quiet grumbling in the community.
Things seem a bit different with the April 2011 CPU. One of the bugs (CVE-2010-0903) was very similar in nature and exploit method to the last Oracle patch release (CVE-2011-0806), but had a dramatically lower risk score. The modification to the CVSS security score was based on Oracle’s modification to the CVSS scoring system to include a ‘Partial+’ impact metric. I have not spoken to anyone at Oracle about this, so maybe they have a threat model that demonstrates an attacker cannot get out of the compromised database, but I doubt it. It looks like an attempt to “game the system” by producing lower risk scores. Why do I say that? Because a ‘Partial’ reference makes sense if the scope of a vulnerability is localized to a very small part of the database. If it’s the entire database – which is what ‘Partial+’ indicates – pwnage is complete.
Lowering of CVSS scores by saying the compromise is ‘Partial+’, instead of ‘Complete’ deliberately(?) misunderstands the way attackers work. Once they get a foot in the door they will automatically start looking for what to attack next. To reduce the risk score you would need to understand what else would be exposed by exploiting this vulnerability. Most people in IT – if they do a threat analysis at all – do it from the perspective of before the exploit. Few fully consider the scope of potential damage if the database were compromised and used against you. I can’t see how ‘Partial+’ makes things better or provides more accurate reporting, but it’s certainly possible the Oracle team has some rationale for the change I have not thought of. To me, though Partial+ means a database is an attacker platform for launching new attacks. And if you have been following any of the breach reports lately, you know most involve a chain of vulnerabilities and weaknesses strung together.
Does this change make sense to you?