Flaw opens door in Windows, Mac, Linux

Security researchers have warned of a flaw in communications software that could allow attackers to take over computers running Windows, Mac OS X and Unix-based operating systems, as well as those with Kerberos authentication systems.

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The problem is widespread because it affects some implementations of XDR (external data representation) libraries, used by many applications as a way of sending data from one system process to another regardless of the system's architecture. The affected libraries are derived from Sun Microsystems' popular SunRPC remote procedure call technology.

The Computer Emergency Response Team (CERT) Coordination Center, a security network based at Carnegie Mellon University, warned on Tuesday that systems using the affected code should immediately apply patches or disable the affected services.

A function in Sun's XDR library contains an integer overflow that can lead to buffer overflows, according to CERT security researchers Jeffrey Havrilla and Cory Cohen. These buffer overflows can allow an attacker to crash a system, execute malicious code or steal sensitive information, Havrilla and Cohen said.

The problem also affects the administration system of Kerberos 5, a widely used network security tool, which could allow attackers to gain control of Kerberos Key Distribution Center authentication functions. This could allow an attacker to gain false authentication with other services. Kerberos is included in Windows 2000.

The MIT Kerberos development team issued a warning and patch on its Web site.

Apple Computer confirmed that its Mac OS X operating system contains the vulnerability, which has been fixed through a recent security advisory, available through the software's automatic update mechanism.

Several sellers of Unix and Unix-like operating systems, including Red Hat, Debian, FreeBSD, Sun and NetBSD, said that their software was affected by the issue, and issued fixes. HP said it was investigating the bug's impact.

Microsoft said it is still investigating how Windows is affected by the problem.

The relevant patches are available from the companies' Web sites, or through the CERT advisory on its Web site.