Re: [bitfolk] 21 critical Exim security issues need addressing

Hi, TL;DR: There's 21 serious security vulnerabilities recently published for the Exim mail server, 10 of which are remotely triggerable. Anyone running Exim needs to patch it ASAP or risk having their server automatically root compromised as soon as an exploit is cooked up. Which may have happened already. Details: https://lwn.net/Articles/855282/ We don't usually post about other vendors' security issues on the announce@ list but I'm making an exception for this one because Exim is installed by default on all versions of Debian, and more than 60% of BitFolk customers use some version of Debian. If you're running Exim you need to upgrade it immediately. Package updates have already been posted for Debian 9 and 10 (stretch/oldstable and buster/stable). The last time this sort of thing happened with Exim several customers were automatically compromised. As it's a root level compromise, if it happens to you then you will never be sure what exactly what done to your server. You might end up needing to reinstall it. Most hosts, unless they are acting as a server listed in one or more domains' MX records, do not need to be remotely accessible on port 25. If that's the case for you then you would be well advised to reconfigure Exim to only listen on localhost. Though there are still 11 other vulnerabilities that local users could exploit. At least you'd only get rooted by a friend, right? An exploit hasn't been published yet but that doesn't mean that one doesn't exist, and now that the source changes are public it should be fairly easy for developers to work out how to do it. Some of the bugs go back to 2004 so basically every Exim install is at risk. If you are running a release of Debian prior to version 9 (stretch) then it's out of security support and may not ever see an updated package for this, so you need to strongly consider turning off any Exim server and doing an OS upgrade before you turn it back on. If you need help, you could reply to this and seek help from other customers, or BitFolk can help you as a consultancy service, but you probably don't want to pay consultancy prices and in any moderately complicated setup our approach is going to be an OS upgrade anyway. Email support(a)bitfolk.com to discuss if still interested in that. Best of luck with the upgrading! Andy -- https://bitfolk.com/ -- No-nonsense VPS hosting

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