Microsoft has warned of a potentially devastating security vulnerability involving its popular Outlook and Outlook Express email clients. It could allow attackers to trick users into running malicious code so giving them control of a victim's machine.
The security bug concerns the vCard, or virtual business cards, component of Outlook, which has been found by @Stake, a firm of security researchers and consultants, to contain a buffer overflow vulnerability.
By creating a vCard doctored with malicious code an attacker could either cause a mail client to crash, or far more seriously, could cause the mail client to run arbitrary hostile code on a victim's machine.
In a security notice on the problem, Microsoft admitted: "Such code could take any desired action, limited only by the permissions of the recipient on the machine.
"It could take any action the user himself could take, including adding, changing or deleting data, communicating with web sites, reformatting the disk drive, and other actions."
vCards arrive at a users machine as email attachments and Microsoft has said the vulnerability is mitigated by the fact a user would have to open an affected attachment or drag it into his contacts book to be affected. However the problem is still serious enough for Microsoft to recommend that all Outlook users should consider updating their browser with a patch.
The affected component is part of Outlook Express, which ships as part of Internet Explorer, so a browser upgrade, not just a patch for the mail client, is needed in order to plug the security hole. Because Outlook uses the same affected component it is also affected by the problem. ®