It has come to the attention of The Exim Maintainers that there is
an exploit circulating in the wild which affects versions of Exim
versions 4.69 and below -- Exim 4.70 was released in November 2009.
The flaw permits remote code execution over SMTP and, when combined
with some clever abuse of Exim's configuration, escalation to root
privileges from the Exim run-time user. [1]
The 4.72 release from June 2010 was also a security-fix release,
for some lesser problems [4]. We suggest that this is the release
that is safest for deployment.
We encourage all Exim users to remain up-to-date with Exim
releases. The exim-announce list [2] is a low-volume moderated list
which announces new releases.
We regret that the full impact of the problem fixed in 4.70 was not
appreciated and that we did not draw more attention to it than the
ChangeLog notice "Potential buffer overflow in string_format". With
more pro-active notification on our part, vendors who package old
releases and backport minimal fixes may have included this fix too.
We expect that the 4.73 release of Exim will include changes that
protect against the privilege escalation seen in the exploit. Some
of the changes in behaviour may cause issues in certain
configurations and there may be configuration changes required as a
result; we take pride in retaining full backwards compatibility of
configurations within a major number, but we are prepared to make
an exception in this case.
As always, full details of changes will be listed in "NewStuff" and
"ChangeLog" and we shall, for the 4.73 release, explicitly detail
what changes in behaviour may cause issues.
We'd like to thank Eugene Bujak for noticing and patching the
problem originally and Sergey Kononenko for reporting the active
exploit. Thanks are due to Intel, UC Berkeley, Red Hat and Astaro
AG for their work to identify the problem exploited and their work
on fixes for 4.73.
This is an update to the earlier notification [3] sent to the
exim-dev list.
Regards,
Nigel Metheringham
pp The Exim Maintainers
[1] CVE-2010-4344 exim remote code execution flaw
CVE-2010-4345 exim privilege escalation
[2] http://www.exim.org/mailman/listinfo/exim-announce
[3] http://www.exim.org/lurker/message/20101210.164935.385e04d0.en.html
[4] CVE-2010-2023 Exim world-writable mail directory with sticky-bit
CVE-2010-2024 Exim MBX locking race condition
