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One of our readers wrote in to let us know that he had received an attempted Exim/Dovecot exploit attempt against his email server. The exploit partially looked like this:
(Obviously edited for your safety, and I didn't post the whole thing.) This is an exploit against Dovecot that is using the feature "use_shell" against itself. This feature, unfortunately, is found in the example wiki on Dovecot's website, and also in their example configuration. We'd caution anyone that is using Dovecot to take a look at their configuration and make use they aren't using the "use_shell" parameter. Or if you are, make darn sure you know what you are doing, and how to defend yourself. -- Joel Esler | http://blog.joelesler.net | http://twitter.com/joelesler |
Joel 454 Posts ISC Handler |
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Jun 7th 2013 6 years ago |
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To be clear, this is about configurations using dovecot as a LDA, and it's actually the exim config to enable that which has the 'use_shell' issue. So if you're checking it should be /etc/exim4/exim4.conf, or similar, that you look at, not the dovecot config!
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Athanasius 7 Posts |
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Jun 7th 2013 6 years ago |
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This must have been going on for some time, as I recall seeing an example of this some weeks ago. It actually got delivered to an administrator account like postmaster@ and seemed like spam at first glance. Unfortunately I can't find a sample of this now. I didn't realise at the time what it was trying to exploit; I'd thought it was maybe something to do with mail sieve/filters like procmail.
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Steven C. 171 Posts |
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Jun 7th 2013 6 years ago |
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