Sendmail: Denial of Service — GLSA 200606-19

Faulty multipart MIME messages can cause forked Sendmail processes to crash.

Affected Packages

mail-mta/sendmail on all architectures
Affected versions < 8.13.6-r1
Unaffected versions >= 8.13.6-r1

Background

Sendmail is a popular mail transfer agent (MTA).

Description

Frank Sheiness discovered that the mime8to7() function can recurse endlessly during the decoding of multipart MIME messages until the stack of the process is filled and the process crashes.

Impact

By sending specially crafted multipart MIME messages, a remote attacker can cause a subprocess forked by Sendmail to crash. If Sendmail is not set to use a randomized queue processing, the attack will effectively halt the delivery of queued mails as well as the malformed one, incoming mail delivered interactively is not affected. Additionally, on systems where core dumps with an individual naming scheme (like "core.pid") are enabled, a filesystem may fill up with core dumps. Core dumps are disabled by default in Gentoo.

Workaround

The Sendmail 8.13.7 release information offers some workarounds, please see the Reference below. Note that the issue has actually been fixed in the 8.13.6-r1 ebuild.

Resolution

All Sendmail users should upgrade to the latest version:

 # emerge --sync
 # emerge --ask --oneshot --verbose ">=mail-mta/sendmail-8.13.6-r1"

References

Release Date
June 15, 2006

Latest Revision
June 15, 2006: 01

Severity
normal

Exploitable
remote

Bugzilla entries