Security pros warn of critical flaws in Kerberos

Vulnerabilities in technology widely used for network authentication leave computers open to attack.

Robert Lemos
Robert Lemos Staff Writer, CNET News.com
Robert Lemos
covers viruses, worms and other security threats.
2 min read
Vulnerabilities in a technology widely used for network authentication have left computers running Unix, Linux and Apple Computer's Mac OS X potentially open to attack.

The flaws could allow an online intruder to gain access to computers running a security feature known as Kerberos. The vulnerabilities, found by the developers at Sun Microsystems and the Kerberos Team at the Massachusetts Institute of Technology, should be patched as soon as possible, Sam Hartman, engineering lead for the team, said Wednesday.

"I would not expect this to lead to a worm," Hartman said. "Most sites will patch it because patching is easy to do. Whereas, if you do have a compromise, it is a lot of work to recover."

Kerberos is the keystone to security for many networks. The software essentially acts as a gatekeeper, identifying the people who are allowed to access computers in the network and those who are not. That makes the software flaws particularly pernicious.

The flaws, known as double-free vulnerabilities, are caused because a part of the program attempts to free up the same computer memory space twice. Such errors are not as easy to take advantage of as another, more common memory error--the buffer overflow. That gives administrators a little breathing room, Hartman said.

"We have no reason to believe that anyone has produced an exploit program," he said. "Moreover, this is not something where we have seen an attack in the wild."

Kerberos is a building block of many network security devices and software. Microsoft uses the mechanism to control security in its Active Directory authentication. However, the company uses a homegrown version of Kerberos that is not affected by the flaws, Hartman said.

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