Microsoft Exchange hole "critical"

[InfoSec News <isn () c4i org>]

http://news.com.com/2100-1001-928055.html?tag=fd_top

By David Becker 
Staff Writer, CNET News.com
May 29, 2002, 3:30 PM PT

Microsoft on Wednesday issued a security alert about a newly
discovered flaw in its Exchange 2000 e-mail software that could allow
hackers to cripple e-mail servers.

The vulnerability, which Microsoft classified as "critical," affects
e-mail servers running Exchange 2000.

Malformed messages created using RFC 821 and 822, versions of the SMTP
format commonly used by e-mail programs, can cause the CPU of the
server receiving the message to run at 100 percent as it attempts to
read the message. The result would be a denial-of-service attack, with
the affected server unable to do anything until it finishes processing
the message.

Christopher Budd, security program manager at Microsoft's security
response center, said the flaw was assigned a "critical" rating
because once the attack starts, it can't be stopped, even if Exchange
is restarted or the server rebooted.

"Once the process starts, you can't stop it," he said, adding that it
could take a server anywhere from a few seconds to a few hours to
process a message. "The key here is that once the system gets hold of
that message, it's got to deal with it."

The bulletin noted that creating such messages would require
specialized knowledge and software, as common e-mail clients such as
Outlook are incapable of creating RFC 821 or 822 content.

"You'd have to be fairly sophisticated," Budd said. "This is not
something where somebody opens an e-mail client, puts a few bad
characters in a message, and sends it. It would basically require
someone to know the language of SMTP."

Microsoft urged system administrators to promptly patch any Exchange
2000 servers.

Discovery of the flaw was credited to researchers at the Johannes
Gutenberg University in Mainz, Germany.

 


-
ISN is currently hosted by Attrition.org

To unsubscribe email majordomo () attrition org with 'unsubscribe isn'
in the BODY of the mail.