IBM's Lotus Notes messaging software can be compromised by a single maliciously crafted email, according to researchers at Core Security Technologies.

There is a vulnerability in in Autonomy KeyView, software used by Lotus Notes to process Lotus 1-2-3 files, they said. Core's researchers found that when they opened a specially crafted Lotus 1-2-3 email attachment in Lotus Notes, they could run unauthorised software on the PC.

Although details of the flaw have not been published, and it has not been picked up by criminals, a determined attacker could easily write attack code, said Ivan Arce, chief technology officer with Core. That's because there are already a number of known KeyView bugs, so exploit code for similar flaws can easily be found.

"Previously there have been other flaws like this published for the same software development kit," he said. "So anyone keeping track of that could write an exploit pretty quickly."

In the past year, security researchers have increasingly focused on these kinds of vulnerabilities, called file parsing bugs. Improvements in hacking software, called fuzzers, which send a barrage of data to programs in order to see if they can be made to act in unexpected ways, have made this type of research easier.

Just last week, researchers at n.runs, a German security firm, predicted that parsing vulnerabilities in security software could actually make some products less secure. Researchers Thierry Zoller and Sergio Alvarez have found 80 parser bugs in anti-virus software over the past two years. The flaws they've found affect every major anti-virus vendor, and many of them could allow attackers to run unauthorised code on a victim's system, the researchers say.

In fact, Symantec recently acknowledged a bug in the KeyView module used by its Symantec Mail Security software. Arce had not tested Symantec's products for this vulnerability, but he said it was quite possibly vulnerable to the flaw as well.

The flaw probably affects other products, according to security experts, because KeyView - which is used to view and print files in about 300 file formats - is used in many different programs. More than 300 companies, including Symantec and Oracle, have licensed KeyView.

IBM acknowledged the problem in a security alert and is offering a patch for Notes 7 users. For those using an older version of Notes, IBM has suggested several workarounds, including deleting the Windows DLL (dynamic link library) file that is associated with Notes.

Autonomy acquired the KeyView software as part of its $500 million purchase of search software vendor Verity, completed in late 2005.