Dailydave mailing list archives

Re: CVSS is the worst compression algorithm ever


From: Adrian Sanabria <adrian.sanabria () gmail com>
Date: Wed, 9 Jan 2019 08:18:48 -0500

Our pentesters use DREAD, which I think most people have moved on from, but
at least the scoring is clear and consistent.

In addition to CVE being wrong on critical details, I've found that most of
ExploitDB isn't exploits. Many are vulnerability checks and almost all are
incorrectly entered. PrivEsc will be labeled RCE and RCE will be labeled
DoS. It's all a mess. If I had the resources to burn it all down and start
from scratch, I'd do it.

--Adrian

On Tue, Jan 8, 2019, 17:47 Nathaniel Ferguson <jferguson () 126 com wrote:

They use a ton of big words in the paper to call CVSS out and give it a
shellacking. Like most of you, we have extensive use of CVSS in our
consulting practice and I've seen this stuff first hand. CVSS is of course
just a buggy compression algorithm for taking complex qualitative data and
then putting it on a number line.


Over the years I've worked at a few different consultancies and at least
originally basically no one used any sort of standardized metric, the
reports were generally humorous from a technical standpoint as the numbers
were basically just made up and didn't adhere to even basic statistics
methodologies-- we take the X and multiple it by Y and add the Z and
there's your score! Some even plotted them along cartoon looking graphs and
plots and my suspicion was that they were really included to give depth to
the reports and break up the monotony of text on text on text. Oddly, I've
never even worked at a place that described the methodology as outlined in
their reports to their employees leaving some question as to how a
methodology was to be implemented if only the client ever heard about it.

In that sense, CVSS et al make some amount of sense, if nothing else it
standardizes to a common metric and isn't what the sales guy or operations
manager made up. Additionally, what a strange word-- shellacking, there is
no 'k' in the word until its made into a present participle.

The paper has three angles here:
Qualitative mappings into quantitative numbers are a silly thing to do,
like people trying to do "social science" by using SurveyMonkey.

Which is what most people are or were selling.

It's fine to have a lossy compression algorithm that emphasizes certain
aspects of the input signal over others, of course, but an additional
CERT/CC critique is we have no reason to think CVSS does this in any useful
way.

Well there 's a missing line here, you can see it from the way that
client-side attacks perverted the concept of remote and so they made them
remote also instead of adding the new line to the plot. Because of stuff
like this. everything is remote now which limits its usefulness. This
doesn't even touch on the fact that most of the CVE database is basically
wrong from submissions including very limited data, id est "memory
corruption results in a DoS".

Nathaniel

在 2019-01-09 00:14:00,"Dave Aitel" <dave.aitel () cyxtera com> 写道:

I wanted to take a few minutes and do a quick highlight of a paper from
CMU-CERT which I think most people have missed out on:
https://resources.sei.cmu.edu/asset_files/WhitePaper/2018_019_001_538372.pdf
Towards Improving CVSS - resources.sei.cmu.edu
<https://resources.sei.cmu.edu/asset_files/WhitePaper/2018_019_001_538372.pdf>
resources.sei.cmu.edu
SOFTWARE ENGINEERING INSTITUTE | CARNEGIE MELLON UNIVERSITY
REV-03.18.2016.0 Distribution Statement A: Approved for Public Release;
Distribution Is Unlimited TOWARDS IMPROVING CVSS
It's almost as funny a read as their previous best work on how "clientless
HTTPS VPNs are insanely dumb <https://www.kb.cert.org/vuls/id/261869/> what were
you thinking omg?"

They use a ton of big words in the paper to call CVSS out and give it a
shellacking. Like most of you, we have extensive use of CVSS in our
consulting practice and I've seen this stuff first hand. CVSS is of course
just a buggy compression algorithm for taking complex qualitative data and
then putting it on a number line. The paper has three angles here:

   1. Qualitative mappings into quantitative numbers are a silly thing to
   do, like people trying to do "social science" by using SurveyMonkey.
   2. We're pretty sure that the compression algorithm is not, in fact,
   putting higher risk items as bigger numbers, which is the whole point of
   the thing.
   3. Nobody is applying this in any sort of consistent way (which is
   probably impossible) which is ALSO the whole point of the thing.


It's fine to have a lossy compression algorithm that emphasizes certain
aspects of the input signal over others, of course, but an additional
CERT/CC critique is we have no reason to think CVSS does this in any useful
way.


There's definitely people in the CVSS process (who I will avoid calling
out by name) who think ANY quantization is good. But read the paper and
decide for yourself - because these are probably serious issues that are
turning your entire risk org into a Garbage-In-Garbage-Out org...


-dave





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