Since then I've been sending in corrections on a monthly basis, taking into account the worst possible score across all affected platforms (and not how Red Hat products were affected specifically).
For the five months May to September 2007 I looked at 178 vulnerabilities (across all Red Hat products and services). Only 80 were accurate. Corrections were submitted to NVD and they fixed the incorrect CVSS scores on the remaining 98 vulnerabilities.
So, before the corrections, there were 65 issues rated "High" out of 178. After the corrections there are actually only 17 rated "High".
Fortunately the number of corrections needed each month seems to be decreasing, but we'll continue to send in corrections every month. Even with the corrections, the severity rating for a given vulnerability may well vary for the version each vendor ships; so you need to be careful if you are basing your risk assesments soley on the accuracy of third-party severity ratings.
So in two days I've scanned just under 2000 pages; some of it into nice fully-searchable PDF files, and some (the stuff I know I want to be able to see in 10+ years time) in jpeg. I've now got an overheated shredder and little shredded bits of paper everywhere.
Although the scanner doesn't work out-of-the-box with current Linux distributions, it just needs a single line adding to a configuration file and then works perfectly with Red Hat Enterprise Linux (I tried RHEL 5 Client as well as Fedora 7). I've sent it to the maintainer so hopefully future updates to Sane will be able to handle the scanner without any editing.
So if you've got a Fujitsu ScanSnap S510 scanner (I keep typing SnapScan for some reason), and you've got sane-backends installed then the following will get it up and running:
# echo "usb 0x04c5 0x1155" >> /etc/sane.d/fujitsu.confThen you can use any scanning front-end, or from the command line say you wanted to scan at 150dpi colour, double-sided, then use "scanimage -L" to figure out where your scanner is, and replace the 005:004 below with the location:
# scanadf --device fujitsu:libusb:005:004 --source "ADF Duplex" --mode Color -v --resolution 150 --y-resolution 150
Even though I'm not a fan, NVD publish a CVSS score for every issue, security companies are using those scores in their vulnerability feeds to customers, and people are using them for metrics. So it's important that these scores are accurate.
I decided to take a look at how accurate the CVSS scores were, so for every vulnerability we fixed in any Red Hat product for June 2007 examined the CVSS score given by NVD. For each one figuring out if the CVSS base metrics were correct, and where they were not submitting the correction back to NVD. This analysis of the vulnerabilities was based on their possible worst-case threat to all platforms (I didn't adjust the CVSS scores for how the issues affected Red Hat products specifically).
There were 39 total vulnerabilities for which unfortunately only 8 scores were accurate. I submitted corrections to NVD and they fixed the CVSS scores on the remaining 31 vulnerabilities.
20 vulnerabilities ended up moving down in ranking, 6 vulnerabilities moved up, and 5 stayed the same (although the CVSS score changed).
Before the corrections there were 14 issues rated "High" out of 39, after the corrections there are just 3 rated "High".
Those corrections are now live in the NVD, and I really appreciate how quick the folks behind NVD were at checking and making the changes. I've submitted to them corrections for a couple more months too, and I'll write about those when there complete. Unfortunately it does take a lot of time to investigate each issue and do the corrections, so it will limit how far back into 2007 we can correct.
My home automation system is all based around XMPP, with a standard Jabber server to which all the home automation systems connect to share messages. I wrote it like this so that it would be easy to just take some existing Jabber client for a platform and be able to come up with a nice looking front end with minimal effort.
I found Iksemel, a portable C XML parser and protocol library that looked perfect, and it only took a couple of hours to have it ported on the NDS, and a couple more hours to get it working with PAlib for wifi. It's not a generic Jabber chat client, but it wouldn't take too much work to make it into one (although I didn't bother with encryption support so you won't be able to use it with Google talk servers for example). Anyway, the code might save someone a few hours, so I've made the source available.
Common Platform Enumeration (CPE) is a naming scheme designed to combat these inconsistencies, and is part of the 'making security measurable' initiative from Mitre. From today we're supporting CPE in our Security Response Team metrics: we publish a mapping of Red Hat advisories to both CVE and CPE platforms (updated daily) and you can use CPE to filter the metrics. Some examples of CPE names:
cpe://redhat:enterprise_linux:5:server/firefox -- the Firefox browser package on Red Hat Enterprise Linux 5 server.
cpe://redhat:enterprise_linux:3 -- Red Hat Enterprise Linux 3
cpe://redhat/xpdf -- the xpdf package in any Red Hat product.
cpe://redhat:rhel_application_stack:1 -- Red Hat Application Stack version 1
User reports a security vulnerability|
(this includes things later found not to be vulnerabilities)
User is confused because they visited a site "powered by Apache"|
(happens a lot when some phishing or spam points to a site that is taken down and replaced with the default Apache httpd page)
User asks a general product support question||38 (25%)|
User asks a question about old security vulnerabilities||21 (14%)|
User reports being compromised, although non-ASF software was at fault|
(For example through PHP, CGI, other web applications)
That last one is worth restating: in the last 12 months no one who contacted the ASF security team reported a compromise that was found to be caused by ASF software.
The National Vulnerability Database provides a public severity rating for all CVE named vulnerabilities, "Low" "Medium" and "High", which they generate automatically based on the CVSS score their analysts calculate for each issue. I've been interested for some time to see how well those map to the severity ratings that Red Hat give to issues. We use the same ratings and methodology as Microsoft and others use, assigning "Critical" for things that have the ability to be remotely exploited automatically through "Important", "Moderate", to "Low".
Given a thundery Sunday afternoon I took the last 12 months of all possible vulnerabilities affecting Red Hat Enterprise Linux 4 (from 126 advisories across all components) from my metrics page and compared to NVD using their provided XML data files. The result broke down like this:
So that looked okay on the surface; but the diagram above implies that all the issues Red Hat rated as Critical got mapped in NVD to High. But that's not actually the case, and when you look at the breakdown you get this result: (in number of vulnerabilities)
| ||NVD: High||
That shows nearly half of the issues that NVD rated as High actually only affected Red Hat with Moderate or Low severity. Given our policy is to fix the things that are Critical and Important the fastest (and we have a pretty impressive record for fixing critical issues), it's no wonder that recent vulnerability studies that use the NVD mapping when analysing Red Hat vulnerabilities have some significant data errors.
I wasn't actually surprised that there are so many differences: my hypothesis is that many of the errors are due to the nature of how vulnerabilities affect open source software. Take for example the Apache HTTP server. Lots of companies ship Apache in their products, but all ship different versions with different defaults on different operating systems for different architecture compiled with different compilers using different compiler options. Many Apache vulnerabilities over the years have affected different platforms in significantly different ways. We've seen an Apache vulnerability that leads to arbitrary code execution on older FreeBSD, that causes a denial of service on Windows, but that was unexploitable on Linux for example. But it has a single CVE identifier.
So if you're using a version of the Apache web server you got with your Red Hat Enterprise Linux distribution then you need to rely on Red Hat to tell you how the issue affects the version they gave you -- in the same way you rely on them to give you an update to correct the issue.
I did also spot a few instances where the CVSS score for a given vulnerability was not correctly coded. CVSS version 2 was released last week and once NVD is based on the new version I'll redo this analysis and spend more time submitting corrections to any obvious mistakes.
But in summary: for multi-vendor software the severity rating for a given vulnerability may very well be different for each vendors version. This is a level of detail that vulnerability databases such as NVD don't currently capture; so you need to be careful if you are relying on the accuracy of third party severity ratings.
I've separated the bars into two sections; the red sections are where we get notice of a security issue in advance of it being public (where we are told about the issue 'under embargo'). The grey sections are where we are reacting to issues that are already public.
The number of issues through researchers and co-ordination centers seem lower than perhaps expected, this is because in many cases the researcher will tell a group such as vendor-sec rather than each distributor separately, or the upstream project directly.