Memory-hogging bug offers universal browser crash exploit

DOM and dumber

Security researchers have published details of a security flaw that can crash multiple browsers across multiple platforms.

There are many more flaws out there that are more serious, but the security shortcomings in JavaScript's DOM (Document Object Model) are nonetheless noteworthy because the issue affects Firefox, Safari, Opera, Chrome and Internet Explorer to a lesser or greater extent. Even smartphones, such as the iPhone and Nokia N95, as well at the Sony PS3 might be forced to crash using the approach, obliging users to reset devices.

The flaw works by tricking a browser into allocating huge chunks of memory, behaviour likely to result in a crash.

Using JavaScript's DOM (Document Object Model) to create a selection menu on a web page with a very high value sets up the trick. H Security explains that the coding trickery results in a huge allocation of memory.

This isn't in itself a problem if the memory area is defined as read only, but problems arise in the many cases where browsers fail to stop overwrites, leading to two processes trying to get at the same portion of memory at the same time and therefore provoking browser crashes.

The flaw presents a browser crash rather than malware injection risk in all cases. Crashing is most easily achieved on IE, with all versions of Microsoft's browser affected. Versions of Ubuntu running Konquerer might be forced to reboot if exposed to attacks based on the bug because of a memory management failure issue.

By contrast Opera, Chrome and Firefox have all been patched to defend against the flaw - so only older versions of those browsers are affected.

A security advisory from G-Sec, including proof of concept code, explains the issue in far greater depth here. ®