GadgetToJScript VS CSS-Exchange

I'm sorry but most of this is not right. We can see in the attacker is running JScript code in memory using the eval function. There are no files dropped to disk and no child processes spawned here -- it's all in memory and all still inside the exchange web server process. At this point, it's impossible to know what JScript was executed, but it is possible (and not that difficult) to run whole .NET programs using JScript. From .NET there's nothing an attacker can't do. They could have easily run a beacon inside of the exchange webserver process without any files dropped to disk or processes spawned.

The MaxServicePointIdleTime property I changed because of what I saw suggested here: https://github.com/microsoft/CSS-Exchange/issues/1581.

This is actively exploited, patch immediately. Microsoft also provided a script that checks Exchange items for malicious messaging items: https://github.com/microsoft/CSS-Exchange/blob/a4c096e8b6e6eddeba2f42910f165681ed64adf7/docs/Security/CVE-2023-23397.md

Microsoft has released a PowerShell script that can be run on Exchange infrastructure to scan email files for malicious UNC paths, however, patching is the preferred mitigation strategy.

I would expect that installing the URL Rewrite 2 module shouldn't cause any problems -- E2013 as such doesn't care about it. In fact, Microsoft's own EOMT script for the Hafnium mitigations suggests installing it. It'll likely require a reboot, though, or at the very least an IIS restart.

Yep, the August security update and OS updates were installed on all four nodes. But the order in which they were installed may have been different... I don't recall. Someone just posted above that this is a known problem with Windows 2012/R2: https://github.com/microsoft/CSS-Exchange/pull/1166

Which is the latest I can find on Github. This server is running Exchange 2019 CU 11. It has the March updates (KB5012698), but not the May one (KB5014261). You can also verify from the build number it's not up to date. There are no vulnerabilities reported and the only thing in "red" is that TCP keepalive warning.

https://github.com/microsoft/CSS-Exchange/issues/535 Even the maintainer David Paulson of the ExchangeHealtcheck script opened an issue on this matter, only waiting on feedback of the Exchange Team.