Weakness endangers Net e-mail, patches available

Security experts today announced the availability of patches to fix what is being called a critical vulnerability in the world's most popular e-mail transfer agent.

The vulnerability affects both open-source and commercial versions of the Sendmail Mail Transfer Agent, which is installed on more than 1.5 million systems connected to the Internet and has been reported to handle from 50 percent to 75 percent of Internet e-mail traffic.

Since the buffer overflow flaw was discovered Feb. 13 by researchers at Internet Security Systems Inc. of Atlanta, developers and distributors of the software have worked to create software patches.

Patches are available for open source versions at www.sendmail.org and for commercial versions from www.sendmail.com and from other vendors.

At the time of today's announcement, no evidence had been found that an exploit for the vulnerability had been created. But security experts urged fast action to fix the flaw.

"Sendmail is too big a target for attackers to ignore, so it makes sense to act immediately to protect your systems," the SANS Institute of Bethesda, Md., said in a statement.

The vulnerability was the first test of the cyberresponse capabilities of the new Homeland Security Department. HSD and White House officials helped coordinate the response, according to ISS.

The vulnerability is in a security check used by Sendmail to validate addresses, either "to" or "from," in e-mail header fields. A specially malformed address could trigger a buffer overflow and give an attacker root access to affected servers. Sendmail versions from 5.79 to the current 8.12.7 are vulnerable.

Effects of a successful attack could be extreme latency or unavailability of affected servers and compromised data integrity in incoming and outgoing traffic.

Sendmail advises users either to upgrade to Version 8.12.8 or to apply the appropriate patch to the earlier versions.

ISS began notifying vendors immediately upon confirming the vulnerability and contacted HSD and the White House Office of Homeland Security on Feb. 14, the company said. Major Sendmail distributors, including Hewlett-Packard Co., IBM Corp., the Sendmail Consortium, SGI and Sun Microsystems Inc., began working on fixes. On the federal side, the Defense Department, Federal CIO Council, Federal Computer Incident Response Team, and Office of Management and Budget were added to the coordinating team.

The Common Vulnerabilities and Exposures project has assigned the identifier CAN-2002-1337 to the vulnerability, which is being evaluated for inclusion in the CVE list on the Web at cve.mitre.org.

Original plans called for announcing the vulnerability last week, but some smaller developers and distributors had not completed work on patches. Because monitoring of hacker chats showed no discussion of an exploit for the vulnerability and sensors detected no exploits in the wild, the announcement was delayed until today.

Information on the vulnerability is available at www.fedcirc.gov, at www.cert.org/advisories/CA-2003-07.html and www.iss.net.