SFOS and SG UTM affected by SMTP/EXIM CVE-2023-51766?

one correction, I suspect that my UTM may have validated SPF against itself for the smuggled emails - but I didn't dig into this further at the time (apologies fror any confusion).

Could you send me via PM the POC Code you used? 
Because as far as i understand you, i should be able to reproduce it with your exact examples: one non existing Email and a SPF record from you. 

I was watching the entire CCC webinar and checked for the logic behind this attack and from what i could see, SFOS and UTM did a SPF check for each indiviual Email generated by this PoC code: https://github.com/duy-31/CVE-2023-51764/ So as soon as SFOS / UTM threats those emails individually (and check for SPF) it should not be affected (by my understanding). 

See: https://youtu.be/V8KPV96g1To 

Hi Seth! Daniel here, an engineer from the email team at Sophos.

Based on the information provided I can't confirm that you induced SMTP smuggling. You say the following:

"if valid SPF exists it can impact the smuggling of the emails, however, if you were to disable SPF for the originating sender IP it should then process fine."

The point of the exploit as explained in the CCC webinar is that the smuggled emails bypass the SPF check because it only checks the first email. In your case, SPF checks run for every domain and as you say, block them. 

Another thing that can cause confusion is softfail: SPF checks can result in softfail if the SPF record is created with "~all" instead of "-all". SFOS doesn't block this result, so it can seem as if the SPF check didn't work or smuggling was successful. 

Nevertheless, I would be happy to investigate further if you provide me with an access ID and logs of the issue happening. If SMTP and exim debug logs are enabled it will be quite easy to see if the exploit worked or not.

I have included the ticket number already, but here it is again: 07155188. I have updated the support ticket with a link to this thread and asked if I can report a complaint about the handle time of 2 weeks for a possible zero day issue. Probably lead to nothing, but I will report any progress here.

Happy to provide further information let me know what log files you need, and any changes to initate debug logs.

Can you share (via PM) your Examples, you used for the PoC Code? So we can reproduce it? 

Hi Seth!

Here's how you can help:

1. Give me an access ID to your system like so: https://doc.sophos.com/nsg/sophos-firewall/18.5/Help/en-us/webhelp/onlinehelp/AdministratorHelp/Diagnostics/ConnectionList/SupportAccess/index.html
   This is just so I can check out your configuration. (You might not be able to do this. In that case, you could send me screenshots of the Policies & exceptions section of your SFOS Email page, as well all the policies and exceptions you have configured.)
2. Run another test and collect debug logs. You can do this like so:
   
   1. Get everything set so all you have to do is send the email.
   2. In the admin console, write the following commands:
      1. service -ds nosync smtpd:debug
      2. service -ds nosync smtpd:exim_debug
   3. Attempt to send the smuggled mail.
   4. Run the same commands as before so your logs won't continue to fill with debug lines.
   5. Send over smtpd_main.log found in /log

You can send everything over in a private message.

Also: please remember to turn on SPF for testing. If the smuggled mail can't bypass SPF, then it isn't a case of SMTP smuggling.