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Sicos1977 / MsgKit

A .NET library to make MSG files without the need for Outlook
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'Cannot send this meeting request.' when sending appointment msg file in Outlook 2016 and Outlook from Microsoft 365 Apps for enterprise #94

Closed snieradkiewicz closed 1 year ago

snieradkiewicz commented 1 year ago

Upon generatin appointment from example and then openning it in outlook and clicking [Send] recieving and error message Cannot send this meeting request. From outlook logs we can see an event:

Microsoft Outlook Cannot send this meeting request. P1: 300972 P2: 16.0.16130.20218 P3: P4: 0x80004005

Creating appintment as a draft returns same error message. Tested under different mail servers.

castexyz commented 1 year ago

Same issue here

Sicos1977 commented 1 year ago

I have to dive a little bit deeper into this but first I have some other issues to solve for my #msgreader project

danaug23 commented 1 year ago

I also ran into the same issue. Thanks

AntonVonDelta commented 1 year ago

Is this library safe? Who introduced the vulnerability?

pwnf commented 1 year ago

I suspect folks are trying to use this library to exploit CVE-2023-23397 as per https://www.mdsec.co.uk/2023/03/exploiting-cve-2023-23397-microsoft-outlook-elevation-of-privilege-vulnerability/.

This library is not the vulnerability rather the blog I’ve linked suggests that the “PidLidReminderFileParameter” parameter in outlook meeting objects (and probably other outlook objects that accept a URI controllable by the sender) are the vulnerability. I suspect there’s been an influx of people trying to use this library to exploit the bug. There’s now a much better POC from MDSec written in PowerShell and in any case Microsoft has released a couple of patches.

Sicos1977 commented 1 year ago

It's the same with car manufactures. If somebody uses a car to kill somebody then it is not the manufactures fault but the person that is driving the car. This also goes for much other things.

I originally made this library so that I could make MSG files without needing Outlook on a server (wich is not a good idea). That people use it to try to steal NTLM hashes is not something that is my fault.

AntonVonDelta commented 1 year ago

Thanks for the reply. I freaked out when I saw the big warning on the front page. I thought someone managed to sneak some code inside.

allanstohn commented 9 months ago

I just ran into the same issue as the original topic in this thread. Cannot send this meeting request. I tried to set appointment draft both to true and false. Any ideas, why this is happening.?

Found this thread - https://twitter.com/wdormann/status/1636114137670361091 But no solution.