Security experts have found a flaw in Sendmail's server software that will allow an attacker to hijack a user's personal computer and view sensitive information.

Sendmail Mail Transfer Agent (MTA) is an SMTP server used on mail gateways to route and shuttle e-mail. It is offered as an open source Linux product and in commercial Unix versions: the new flaw affects both.

Internet Security Systems said today the Sendmail exploit is a signal race vulnerability caused by the mishandling of asynchronous signals.

By forcing the SMTP server to timeout at a specific instant, an attacker can run malicious code and: exposure, deletion, or modify programs and data on the system; disrupt e-mail delivery; and view confidential documents.

Because Sendmail starts a new process for each connected computer, attackers can exploit it on any machine connected to Sendmail.

Sendmail said it is not aware of any public exploit code for this vulnerability.

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