Advisory Details

This vulnerability allows network-adjacent attackers to execute arbitrary code on affected installations of Exim libspf2. Authentication is not required to exploit this vulnerability.

The specific flaw exists within the parsing of SPF macros. When parsing SPF macros, the process does not properly validate user-supplied data, which can result in an integer underflow before writing to memory. 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.

• 2022-06-17 - Vulnerability reported to vendor
• 2023-09-27 - Coordinated public release of advisory