This vulnerability allows remote attackers to execute arbitrary code on
affected
installations of Exim. Authentication is not required to exploit this
vulnerability.

The specific flaw exists within the handling of NTLM challenge requests. The
issue results from the lack of proper validation of the length of user-supplied
data prior to copying it to a fixed-length stack-based buffer. An attacker can
leverage this vulnerability to execute code in the context of the service
account.

06/06/22 – ZDI requested a PSIRT contact.

06/14/22 – ZDI reported the vulnerability to the vendor.

04/25/23 – ZDI asked for an update.

04/25/23 – The vendor asked us to re-send the reports.

05/10/23 – ZDI sent the vulnerability to the vendor.

09/25/23 – ZDI asked for an update and informed the vendor that we intend to
publish the case as a zero-day advisory on 09/27/23.

-- Mitigation: Given the nature of the vulnerability, the only salient
mitigation strategy is to restrict interaction with the application.

References:
http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2023-42116