F-Secure has patched several vulnerabilities in its security products, the most critical of which could be used to run unauthorised software on a victim's computer.

The most serious bug affects F-Secure's antivirus products. A flaw in the way the software unpacks files that have been compressed using the LHA archiving format, could allow an attacker to crash the system, or even run unauthorised software on the computer, F-Secure said an advisory.

This flaw is related to a similar flaw in the Gzip decompression utility that was discovered last September, F-Secure said.

Security vendor Secunia ApS rates the bug as highly critical. The flaw affects F-Secure's Anti-Virus, Internet Gatekeeper and Internet Security product suites.

A second less-critical vulnerability in some of the company's antivirus software was also patched Wednesday. This flaw could be used by an attacker with access to the local system to get into unauthorised parts of the system in what is called a privilege escalation attack.

Users of some versions of F-Secure Anti-Virus and Internet Security have been automatically delivered the software patches for these flaws, F-Secure said. A list of which products require hotfixes can be found within F-Secure's security bulletins.

Also on Wednesday, F-Secure fixed a flaw in its Policy Manager Server that could be used by attackers to launch a denial of service attack against the security management software. Secunia rates this bug as "less critical."