Dark Reading is part of the Informa Tech Division of Informa PLC

This site is operated by a business or businesses owned by Informa PLC and all copyright resides with them.Informa PLC's registered office is 5 Howick Place, London SW1P 1WG. Registered in England and Wales. Number 8860726.

Application Security

03:16 AM

Security-Bug Rating System Gets A Makeover

The Common Vulnerability Scoring System will be moving to its third iteration next year, aiming to make the rankings more objective and add more ratings to increase accuracy

In 2005, three companies -- Cisco, Qualys, and Symantec -- announced the Common Vulnerability Scoring System (CVSS) as a way to rank the security impact of software flaws and the potential risks they posed to companies.

In theory, the flaw scoring system aims to give security professionals, researchers, and software vendors a repeatable way to rank the severity of a vulnerability by measuring the issue's base exploitability, how that evolves over time, and the impact the security bug has on the IT environment. While use of the CVSS has grown, especially in government and research circles, a number of shortcomings -- including less-than-objective scoring -- has curtailed its use in commercial settings.

"It is a grand goal to have -- if I look at some data, and you look at some data, and we end up with the same score," says Carsten Eiram, chief research officer for Risk Based Security, a consultancy. "Yet the guidelines are not that clear, so we are seeing inconsistencies."

The Common Vulnerability Scoring System consists of a base score that attempts to measure the severity of a vulnerability, as well as a temporal score that measures the exploitability of an issue over time and an environmental score that measures how dependent a company is on the vulnerable software product. In 2007, the Forum of Incident Response and Security Teams (FIRST), which took over managing the project, released version 2, adding more detailed rankings and attempting to reduce subjective scores.

While the system works fairly well for many vulnerabilities, there are a large number of issues for which the scoring system fails. In an open letter to FIRST, Brian Martin of the Open Security Foundation and Risk Based Security's Eiram, criticized the current iteration of the standards for its tendency to assign similar scores to flaws with significantly different impacts. The use of only three levels of scoring -- none, partial, and complete -- for most vulnerability attributes tends to mean that a vast middle ground gets assigned to a single value: partial. Companies, such as Oracle, have already used a crutch to work around the issue, creating a "partial+" ranking.

The lack of a fine-enough focus is something that FIRST aims to fix in CVSS version 3, says Seth Hanford, chair of the Special Interest Group for CVSS Version 3 at FIRST.

"The CVSS scores don't always line up with reality," he says. "It is hard to score, for example, a bypass of a firewall. It doesn't really affect the host dramatically, but it has a major impact on the business overall."

[A pair of reports look at the trends in vulnerability disclosure over a decade or more. Here are four lessons from the data on more than 50,000 flaws. See Lessons Learned From A Decade Of Vulnerabilities.]

Because scores are calculated from the standpoint, or scope, of the host operating system, vulnerabilities that could impact other systems, or reduce the security posture of an entire network, are difficult to score properly under version 2, Hanford says. The group is creating a number of strategies to better rate vulnerabilities in CVSS version 3, including giving more weight to a "partial" ranking and adding new metrics, such as user interaction and privileges.

Adding more attributes to the scoring system can result in better scores, but could also make the scores more subjective, and subjective ratings are a lot less useful, says Vinnie Liu, a managing partner with consultancy Stach & Liu. An IT security group that uses vulnerability rankings to triage fixes may face pushback from developers, some of whom believe that refuting the rankings is a better use of their time than fixing the issues, Liu says.

"They will bicker over things like that, rather than focus on fixing the problems," he says. "They will focus on how to argue the number down."

FIRST plans to make the Common Vulnerability Scoring System an on-going project: As soon as CVSS version 3 is released, the group will begin work on version 4, FIRST's Hanford says. Threats on the Internet keep changing, which tend to highlight different weaknesses in the system, he says.

"The nature of the threats on the Internet are very different," Hanford says. "With CVSS version 2, we were dealing primarily with network worms."

A draft of version 3 of the Common Vulnerability Scoring System is due by the end of the year, with the final draft schedule to be completed by summer 2014.

Have a comment on this story? Please click "Add Your Comment" below. If you'd like to contact Dark Reading's editors directly, send us a message.

Comment  | 
Print  | 
More Insights
Newest First  |  Oldest First  |  Threaded View
97% of Americans Can't Ace a Basic Security Test
Steve Zurier, Contributing Writer,  5/20/2019
TeamViewer Admits Breach from 2016
Dark Reading Staff 5/20/2019
How a Manufacturing Firm Recovered from a Devastating Ransomware Attack
Kelly Jackson Higgins, Executive Editor at Dark Reading,  5/20/2019
Register for Dark Reading Newsletters
White Papers
Cartoon Contest
Write a Caption, Win a Starbucks Card! Click Here
Latest Comment: This comment is waiting for review by our moderators.
Current Issue
Building and Managing an IT Security Operations Program
As cyber threats grow, many organizations are building security operations centers (SOCs) to improve their defenses. In this Tech Digest you will learn tips on how to get the most out of a SOC in your organization - and what to do if you can't afford to build one.
Flash Poll
Twitter Feed
Dark Reading - Bug Report
Bug Report
Enterprise Vulnerabilities
From DHS/US-CERT's National Vulnerability Database
PUBLISHED: 2019-05-22
Adobe Media Encoder version 13.0.2 has an out-of-bounds read vulnerability. Successful exploitation could lead to information disclosure.
PUBLISHED: 2019-05-22
OX Software GmbH OX App Suite 7.8.4 and earlier is affected by: Information Exposure.
PUBLISHED: 2019-05-22
stack_protect_prologue in cfgexpand.c and stack_protect_epilogue in function.c in GNU Compiler Collection (GCC) 4.1 through 8 (under certain circumstances) generate instruction sequences when targeting ARM targets that spill the address of the stack protector guard, which allows an attacker to bypas...
PUBLISHED: 2019-05-22
Adobe Acrobat and Reader versions 2019.010.20100 and earlier, 2019.010.20099 and earlier, 2017.011.30140 and earlier, 2017.011.30138 and earlier, 2015.006.30495 and earlier, and 2015.006.30493 and earlier have a use after free vulnerability. Successful exploitation could lead to arbitrary code execu...
PUBLISHED: 2019-05-22
Adobe Acrobat and Reader versions 2019.010.20100 and earlier, 2019.010.20099 and earlier, 2017.011.30140 and earlier version, 2017.011.30138 and earlier, 2015.006.30495 and earlier, and 2015.006.30493 and earlier have a use after free vulnerability. Successful exploitation could lead to arbitrary co...