Microsoft released an unscheduled security patch on Friday designed to fix a trio of serious security problems affecting users of its ubiquitous Internet Explorer Web browser. All three of the security vulnerabilities might be exploited to take control of vulnerable systems, so patching is a necessity.
The flaws involve: an integer overflow involving the way IE processes bitmap files, a memory processing vulnerability in the processing of GIF files and a scripting vulnerability that was the basis of June's Download.Ject (Scob) attack. All three of these vulnerabilities have been reported to be relatively straightforward to exploit. "Even vigilant users visiting a malicious website, viewing a malformed image, or reading an HTML-rendered email message may be affected," according to a bulletin from security clearing house US-CERT. No surprise, then, that Redmond gives all three vulnerabilities its dreaded "critical" security classification.
IE versions 5.01, 5.5. and 6 on multiple Windows platforms are affected so it promises to be a busy day for sysadmins everywhere. Early versions of Microsoft's cumulative patch didn't apply the final release code for XP customers running the latest version of Windows Update. After correcting this, Microsoft reissued its advisory on Sunday. The latest version of the bulletin is here.
Last month Microsoft released a tool to clean up machines infected during last month's Download.Ject security flap. Users visiting a website contaminated with Download.Ject activated a script that downloaded a Trojan horse (called Berbew) from a website in Russia. This website was rapidly taken down but the underlying vulnerability in Internet Explorer used in the Download.Ject remained until last weekend despite the earlier availability of a workaround from Microsoft designed to limit the scope for mischief.
Redmond released these configuration changes earlier in July and followed up with a tool to remove variants of the Berbew Trojan from infected systems. Berbew (AKA Webber or Padodor) is capable of extracting passwords and login details from victims and forwarding this confidential data to crackers.
The risk posed by future Download.Ject-style attacks prompted security clearing house US-CERT to advise users to ditch IE for general web browsing, a call since repeated by other security experts. The seriousness of this warning - and the bad publicity it was getting because of the problem prompted Microsoft to break with its normal patch cycle in issuing a fix. Redmond normally issues patches on the second Tuesday of each month. ®