Date: Fri, 24 Nov 2017 22:59:12 -0500 From: Phil Pennock <oss-security-phil@...dhuis.org> To: oss-security@...ts.openwall.com Subject: RCE in Exim reported In Post-Thanksgiving mail-catchup, I see that the Exim Project was gifted with a couple of surprises in our public bugtracker on Thursday morning. Complete with proof-of-concept small Python script. I've requested CVEs, don't have them yet. My mail to our announce list: https://lists.exim.org/lurker/message/20171125.034842.d1d75cac.en.html Remote code execution in the first vulnerability, getting execution as the Exim run-time user. A complete mitigation is to disable advertising the CHUNKING extension, in which case an attempt to use the BDAT verb should result in: 503 BDAT command used when CHUNKING not advertised The instructions I wrote in the mail to our announce-list, were: } With immediate effect, please apply this workaround: if you are running } Exim 4.88 or newer (4.89 is current, 4.90 is upcoming) then in the main } section of your Exim configuration, set: } } chunking_advertise_hosts = } } That's an empty value, nothing on the right of the equals. This } disables advertising the ESMTP CHUNKING extension, making the BDAT verb } unavailable and avoids letting an attacker apply the logic. Chunking support was introduced with Exim 4.88; the current release is 4.89, 4.90 is in RC series now, it looks like a 2-line fix (written by Jeremy Harris) is probably right for the first issue. Public bugtracker links: https://bugs.exim.org/show_bug.cgi?id=2199 https://bugs.exim.org/show_bug.cgi?id=2201 -Phil Download attachment "signature.asc" of type "application/pgp-signature" (997 bytes)
Powered by blists - more mailing lists
Please check out the Open Source Software Security Wiki, which is counterpart to this mailing list.
Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.