The Calgary-based Web site SecurityFocus, which is owned by Symantec, has released a warning about a possible exploit that could affect computers running Apple Computer Inc.s Mac OS X and Mac OS X Server versions 10.0.0 through 10.3.7.
According to the site, “An attacker may leverage this issue to cause a system-wide denial of service or to gain escalated privileges on an affected computer, potentially leading to unauthorized superuser access.”
However, unlike with many recent exploits for Windows-based systems, this vulnerability requires that attackers must have local access to the target computer.
This means that an attacker must already have an account on and access to the computer. As a result, this exploit is not likely to be propagated over the Internet or a network.
“This is not something that can turn into a worm or a widespread threat,” said Oliver Friedrichs, senior manager of the Security Response group at Cupertino, Calif.–based Symantec Corp.
Friedrichs said the exploit could be used over a local or remote network, but only if the attacker already has an account on the target computer. And, he said, Mac OS X does not allow “hidden” accounts on a computer.
“This exploit can be used for a regular user to elevate his access to administrator or superuser,” said Friedrichs. Once the attacker acquires elevated status, he or she can change or modify any data in the system.
However, said Friedrichs, the attacker also has to rely on an existing user with an administrator account to modify a critical system file for the exploit to become active. He added that the attacker must have already manipulated that system file by creating a link in it that directs the system to make changes to the attackers account.
If the attacker fails to properly manipulate the right system file or fails to get a user with administrator privileges to modify this file, the exploit is foiled.
“On a scale of 1 to 10, the severity is 6.9,” Friedrichs said, “but the likelihood is low.” He added that this is not an exploit that can be used on a widespread basis. “These would be one-off attacks,” he said.
“Overall, this is likely to be used in isolated cases where someone specifically knows a computer and wants to gain admin privilege on a system theyve already access to,” he said.
“This type of vulnerability has been seen in Unix environments for decades,” said Friedrichs. “Individual vulnerabilities like this, because of the quantity of source code, tend to creep in.”
SecurityFocus recommends that computer owners allow accounts and access only to people they trust. In addition, SecurityFocus recommends that when not running administrative activities, such as installing some software and disk maintenance, users should work in non-administrative accounts.
Apple representatives did not respond to requests for comments.