On March 2nd, 2021 at ~6pm GMT Microsoft released an out of band update to all version of exchange from 2010 through to 2019. This was in response to a range of vulnerabilities which had been abused (a 0-day) by a threat actor (coined by MS as HAFNIUM).
For more info from MS please see the following:
Key CVES include:
CVE-2021-26855, CVE-2021-26857, CVE-2021-26858, and CVE-2021-27065. Read more “Checking for Hafnium or other groups impact from Exchange Abuse”
With the Hafnium “incidents” and Exchange vulnerabilities I wanted to help people with ruling in or out compromise of their Exchange 2010 environments. At the time of writing, I don’t believe that Hafnium affected Exchange 2010 via the reported kill chain, I believe that BEC would be required but this is a theory, my general view is Exchange 2010 might be ‘safe’ from this kill chain. This is due to the initial stage leveraging CVE-2021-26855 which is an SSRF vulnerability which only affectes the new architecture (2013+). However, this is an unsupported platform so I wanted to help with some baselines and talk about how I would approach ruling compromise in or out (at least with regards to these vulnerabilities). The key impact area is a web shell. I’ve made some baselines to help people look for abnormalities.
This document was made with limited time and without full Whitebox access to source code and engineering expertise. The areas we are checking for IOCs appear to make logical sense, but the OS and APP (Exchange 2010) are unsupported, and we are not the vendor. So, I am afraid your hunting responsibility is on you, this is just my opinions and thoughts from a very fast analysis. Use at your own risk. Read more “Exchange 2010 Rapid Analysis for IOCs”