Feeds

MS Exchange-2K, Excel-XP security warnings

Malicious fun with SMTP and style-sheets

  • alert
  • submit to reddit

Remote control for virtualized desktops

First up we have a potentially crippling exploit with Exchange 2000, in which a malformed mail attribute can spike the system CPU to 100% load while the malicious message is being processed. Re-starting the service or re-booting the Exchange server will not correct it; the process will resume automatically as soon as the service is re-started. Depending on the attacker's ingenuity, a server could be taken down for anywhere from a few seconds to several hours.

The problem lies in the Store function that processes messages, which takes precedence over other Store functions which might otherwise be invoked to clear the offending message, MS says. It was discovered by a team of researchers from Johannes Gutenberg University in Mainz, Germany.

This isn't quite k1dd13 stuff. An attacker would have to create a raw message and establish a direct connection to the target server. It's not something one can accomplish by playing around with an e-mail client; a successful attacker would have to be quite familiar with SMTP, which narrows the threat field.

That being said, the potential for a crippling DoS attack is sufficient for MS to brand this one 'critical', a denomination which it avoids like the plague. As usual the MS bulletin is unbearably vague about what's going on here, with frequent recourse to meaningless generalities like 'a specially malformed attribute'.

On the positive side there's no potential for a system compromise here, Exchange 5.5 is not affected, and there is a patch for 2K posted here. The patch, we're told, will reject messages possessed of those 'specially malformed attributes', whatever they happen to be.

Next up we have a glitch in Excel-XP style sheets, discovered by Georgi Guninski. This is k1dd13 material, so beware. If a user views an .xls file using the XML style sheet, it's quite easy for an attacker to run or call executable code. Guninski gives a harmless example in his advisory, which will simply call a shell and list your directories for you, thus:

xls_sux.xls
<?xml version="1.0"?>
<?xml-stylesheet type="text/xsl" href="#?m$ux" ?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/TR/WD-xsl">
<xsl:script>
<![CDATA[
x=new ActiveXObject("WScript.Shell");
x.Run("%systemroot%\\SYSTEM32\\CMD.EXE /C DIR C:\\ /a /p /s");
]]>
</xsl:script>
<msux>
msux
written by georgi guninski
</msux>
</xsl:stylesheet>

As for the malicious potential here, we'll just leave that to the admirably evil imaginations of our beloved readers.

On the plus side, style sheets are not selected by default, so when the exploit runs, users should be asked if they want to view the file with the style sheet. How many will think, 'yeah, that sounds like an improvement' as opposed to those who will think, 'stuff that Redmond gimmick' we can't guess.

For a workaround, Guninski offers this bit of wisdom: "Power-off the poor Windoze box if you see Excel mentioning style sheets."

We can offer no better advice. ®

Internet Security Threat Report 2014

More from The Register

next story
Be real, Apple: In-app goodie grab games AREN'T FREE – EU
Cupertino stands down after Euro legal threats
Download alert: Nearly ALL top 100 Android, iOS paid apps hacked
Attack of the Clones? Yeah, but much, much scarier – report
You stupid BRICK! PCs running Avast AV can't handle Windows fixes
Fix issued, fingers pointed, forums in flames
Microsoft: Your Linux Docker containers are now OURS to command
New tool lets admins wrangle Linux apps from Windows
Bada-Bing! Mozilla flips Firefox to YAHOO! for search
Microsoft system will be the default for browser in US until 2020
Facebook, working on Facebook at Work, works on Facebook. At Work
You don't want your cat or drunk pics at the office
Soz, web devs: Google snatches its Wallet off the table
Killing off web service in 3 months... but app-happy bonkers are fine
prev story

Whitepapers

Why cloud backup?
Combining the latest advancements in disk-based backup with secure, integrated, cloud technologies offer organizations fast and assured recovery of their critical enterprise data.
Forging a new future with identity relationship management
Learn about ForgeRock's next generation IRM platform and how it is designed to empower CEOS's and enterprises to engage with consumers.
How to determine if cloud backup is right for your servers
Two key factors, technical feasibility and TCO economics, that backup and IT operations managers should consider when assessing cloud backup.
Reg Reader Research: SaaS based Email and Office Productivity Tools
Read this Reg reader report which provides advice and guidance for SMBs towards the use of SaaS based email and Office productivity tools.
Getting ahead of the compliance curve
Learn about new services that make it easy to discover and manage certificates across the enterprise and how to get ahead of the compliance curve.