CVE-2014-2972: Medium severity sa-exim vulnerability

As reported to the exim user's mailing list [1], Exim suffers from a local vulnerability where a string expansion is evaluated twice. If a local attacker were able to provide unsanitized data to a data source used by Exim for looking up a value, in certain situations, the data would be eval()'d twice. This is not remotely exploitable and requires a user account on the Exim server, and an Exim configuration that does lookups against files to which the user has edit access. The end result is that, if the conditions are true, arbitrary code could be executed as the exim user. As described in the posting:

""" The root cause of this issue is the arguments to mathematical comparison operations are expanded twice (<, <=, >, >=, =). The intent of the original code was the first expansion could (for example) lookup an item from a file. The assumption was that entry would be some form of valid integer so that value was then passed to the expand function again to do a numeric conversion of values such as 19k or 45M to integers. However, if the content of the lookup is under direct user control, they could insert something with an expansion, such as:

${run {/bin/touch /tmp/OUCH}}

Since the data is not sanitized when the second expansion occurs (intended to process numerical conversion), that command would get executed as the exim user. """

This is corrected in the Exim 4.83 release [2],[3],[4]. From the description, it looks as though every version of Exim released since 2004 is affected.

[1] https://lists.exim.org/lurker/message/20140722.152452.d6c019e8.en.html [2] http://git.exim.org/exim.git/blob/exim-483:/doc/doc-txt/ChangeLog [3] http://git.exim.org/exim.git/commitdiff/7685ce68148a083d7759e78d01aa5198fc099c44 [4] http://git.exim.org/exim.git/commitdiff/0de7239e563eff6e83c3e72d7deb9fd26a54a3a7