Patching Procedure vs. Exploitation Potential

By eric

When you talk to many security experts, they pretty much agree that when a vulnerability hits, that it’s necessary that it be patched and that its only a matter of time until the sh*t hits the fan and some real knowledgable black hat has put something together for the script kiddies to play with. But a lot of people seem to forget every time a patch is required on a production system that there is due process that system administrators must go through. One of the primary steps is simply evaluation.

The primary questions that needs to be evaluated are:

What is the likelihood of the vulnerability being exploited or the damage that could be caused if it is exploited?

vs.

How long will it take to apply the patch, test it, implement it, then deploy it to the production environment? What kind of impact will that have on the production servers in terms of outages/downtime? Will it break anything else?

Let’s take some time to break these down. I have always found that the easiest way for most people to understand a problem is to use an example. I don’t want to single out phpBB, but since it recently came up and spurred a necessary conversation, I will use it for my example. The advisory that I am referencing is available here from Bugtraq.

At one of the many websites I run, I administer a phpBB forum. The forum is relatively low volume, but high volume enough to attract spammers which means its likely that it also attracts hackers (of the black hat variety). The phpBB version is 2.0.21. For a few reasons, we have not only modified some of the source code of phpBB, but we have also added plugins. For anyone who has any experience adding plugins into phpBB, you know that its akin to chewing glass (to say the least). Even though we version track in CVS, it would still be somewhat of a PITA to update to 2.0.22. The process would be something along the lines of:

Import the new version into the old version with the changes into CVS. See if it makes sense to resolve the conflicts. If so, resolve the conflicts and begin testing. If not, figure out how to duplicate the changes in the previous version (2.0.21) in the new version (2.0.22). Once that’s been done, then add the plugins that were installed in the old version into the new version. Come up with a transition plan for the production server. Back up the data and do a few test runs of the transition on the development box. Then schedule the outage time and do the turnover to the new server. Then pray everything goes ok for the transition. Simple, No?

The point of going through that lengthy explanation was to demonstrate that the upgrade process may not be as simple (in a lot of cases) as:

1
apt-get update && apt-get upgrade

The exploit itself requires a user to create a shockwave flash file with certain parameters, then put it into a specific web page with certain parameters, and then it must be private messaged (emailed) to someone who is already signed into the board (has an active cookie).

Many security experts would tell you that, “It’s a vulnerability, it needs to be patched immediately.” Well, let’s do that evaluation thing I was referring to earlier. How likely is it that someone is going to take the time to create that flash file. And even if someone does go to that trouble, what’s to say that if a user (or the admin) receives the message in an email, that they are going to visit the site and watch the video?

My colleague was asserting that it’s out there on the internet and needs to be protected. And to that extent, I certainly agree. However, the amount of time that it would take to make all those changes, test them, and deploy the changes to the production server far outweighs the possibility of the application being exploited.

When I first started out in security, I took the approach, “It’s a vulnerability…Security at all costs.” Now I have learned that sometimes one needs to balance out time vs. need vs. priority. So I encourage System Administrators to think before jumping into situations like that. Think of how much more work could be accomplished in the time that would have been spent trying to patch something that probably wouldn’t have been exploited to begin with.

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