Critical Exim bug bypasses security filters on 1.5 million mail servers

CVE-2024-39929 is a critical Exim MTA vulnerability (affecting releases up to 4.97.1) that permits attackers to bypass the mime_filename extension-blocking mechanism and deliver executable attachments into user mailboxes; Exim released a patch on July 10, 2024, Censys observed ~1.57M potentially vulnerable public servers, and a PoC is available though no active exploitation is reported — administrators should patch or restrict remote access to affected servers.