FTP software flaw could allow remote attacks on servers

Computerworld - Security analysts are warning about a software flaw that they said could allow intruders to gain unauthorized access to remote file transfer protocol (FTP) servers.

In an advisory issued yesterday, Network Associates Inc.'s PGP Security division said the problem is related to the "globbing" command used in Unix shells. The command essentially acts as a path name generator, allowing users to search for multiple file names by entering shorthand commands that are then used by the software to search for common patterns.

Santa Clara, Calif.-based PGP said its Computer Vulnerability Emergency Response Team found a flaw that allows the pattern expansion done through the glob function to instead be directed to cause various buffer overflows in FTP servers -- a capability that could enable malicious attackers to gain root-level privileges on affected systems.

While potentially dangerous, the problem is said to usually only affect FTP servers that give remote users the ability to create directories on the system hosting the FTP daemon. That will likely restrict the vulnerability's threat, said Greg Shipley, security services director at Chicago-based network and security consulting firm Neohapsis Inc.

"The vast majority of FTP servers out on the Internet don't allow users to create directories," Shipley said. "It could pose a significant threat, but it remains to be seen how many of these FTP servers are going to be affected."

A half-dozen versions of Unix have been confirmed to include vulnerable FTP daemons that could be used to exploit the globbing flaw, according to PGP. The operating systems in question include Hewlett-Packard Co.'s HP-UX 11, Silicon Graphics Inc.'s Irix 6.5.x and Sun Microsystems Inc.'s Solaris 8, plus FreeBSD 4.2, OpenBSD 2.8 and NetBSD 1.5.

Since FTP is the primary method of transferring files over the Internet and is used on many servers in default configurations, the problem could allow intruders to take control of the affected servers, PGP said in a separate announcement that was released today.

"In addition to the threat of data loss or attacks against private networks, many Web server administrators rely on FTP to post content to their Web servers," said Jim Magdych, manager of the emergency response team at PGP. "These vulnerabilities could offer an easy avenue of approach for an attacker intent on defacing Web sites."

The CERT Coordination Center at Carnegie Mellon University in Pittsburgh also posted a notice about the FTP flaw on its Web site today. The buffer management flaw could let intruders execute arbitrary code on an FTP server and "may be confused with a