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Software flaw threatens Linux servers

A vulnerability in the widely used FTP server leaves numerous sites open to online attackers. The situation worsens when Red Hat mistakenly releases information on the flaw.

A vulnerability in the most widely used FTP server program for Linux has left numerous sites open to online attackers, a situation worsened when Red Hat mistakenly released information on the flaw early, leaving other Linux companies scrambling to get a fix out.

"Other vendors didn't have a patch," said Alfred Huger, vice president of engineering for network security information provider SecurityFocus. The company has been working with vendors to fix the vulnerability after computer security company Core Security Technologies alerted them to the problem Nov. 14.

"The fix is not rocket science," Huger said. "But we weren't working at a breakneck pace to get a patch out, because everyone was working together."

The software flaw affects all versions of wu-FTP, a program originally created at Washington University at St. Louis for servers running FTP (file transfer protocol) functions for transferring files over the Internet.

While the exact number of active FTP servers on the Internet is not known, the software is the most commonly installed file server and accompanies most major Linux distributions, including those from Red Hat, SuSE, Caldera International, Turbolinux, Connectiva, Cobalt Networks, MandrakeSoft and Wirex.

The problem, known in security circles as the wu-FTP Globbing Heap Corruption Vulnerability, allows attackers to get remote access to all files on a server, provided they can access the FTP service. Since most such servers provide anonymous access to anyone on the Internet, a great number will be vulnerable.

Huger called the flaw "serious."

The impact of the software vulnerability was exacerbated because many Linux software companies were caught flat-footed by a surprise early release of information regarding the vulnerability.

The group that discovered the flaw, Core ST, informed Linux software companies and the open-source group that manages development for wu-FTP of the vulnerability in mid-November. On Tuesday, however, while the companies were working together on a fix, Red Hat mistakenly released a security advisory to its own customers, almost a week early.

Normally, an advisory is a good thing, but other Linux software sellers had expected any advisories to be published Dec. 3, giving them time to work on fixes. Instead, the surprise announcement left the customers of other companies' products vulnerable.

"When I noticed on Bugtraq this morning, it was a big surprise to me, and I'm sure that other companies were caught without a patch as well," said Vincent Danen, security updates manager for French Linux maker MandrakeSoft.

Since Mandrake Linux 8.0--the current version is 8.1--the company has used a different FTP program, ProFTP, so Danen was unsure how many Mandrake users would be affected by the flaw.

The company has completed its own patch for Mandrake Linux but still has to test it more fully, said Danen, who expected it to be ready on Monday. "Red Hat didn't do anyone any favors with this."

On Wednesday, both SuSE, whose current distribution doesn't use wu-FTP as a default, and Caldera released advisories and patches.

Ivan Arce, chief technology officer for Core ST, said that the early release by Red Hat has hurt security.

"The early release caught (software makers) in the middle of the testing process," he said. "They had to scramble to get their fixes ready and tested for all the vulnerable distributions. Some vendors have up to 25 different distributions that are vulnerable and as you can imagine regression testing for all of them is not quick."

Meanwhile, he added, end users know they are vulnerable but don't have a patch to apply.

For its part, Red Hat apologized for the problem.

"We were releasing some advisories on the same day, and an overzealous administrator pushed this out as well," said Mark Cox, senior engineering director for Red Hat. The company is adding new safeguards to its publishing system to avoid similar problems in the future, he said.

"We put a stop to this," Cox said. "This will not happen again. It was a bad mistake."