Security News > 2024 > July > Critical Exim bug bypasses security filters on 1.5 million mail servers
Censys warns that over 1.5 million Exim mail transfer agent instances are unpatched against a critical vulnerability that lets threat actors bypass security filters.
Tracked as CVE-2024-39929 and patched by Exim developers on Wednesday, the security flaw impacts Exim releases up to and including version 4.97.1.
According to the survey, over 59% of the 409,255 mail servers reachable on the Internet during the survey were running Exim, representing just over 241,000 Exim instances.
Per a Shodan search, over 3.3 million Exim servers are currently exposed online, most in the United States, followed by Russia and the Netherlands.
The National Security Agency revealed in May 2020 that the notorious Russian military hacking group Sandworm has been exploiting a critical CVE-2019-10149 Exim flaw since at least August 2019.
More recently, in October, the Exim devs patched three zero-days disclosed through Trend Micro's Zero Day Initiative, one of them exposing millions of Internet-exposed Exim servers to pre-auth RCE attacks.
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Related Vulnerability
| DATE | CVE | VULNERABILITY TITLE | RISK |
|---|---|---|---|
| 2024-07-04 | CVE-2024-39929 | Exim through 4.97.1 misparses a multiline RFC 2231 header filename, and thus remote attackers can bypass a $mime_filename extension-blocking protection mechanism, and potentially deliver executable attachments to the mailboxes of end users. | 0.0 |
| 2019-06-05 | CVE-2019-10149 | OS Command Injection vulnerability in multiple products A flaw was found in Exim versions 4.87 to 4.91 (inclusive). | 9.8 |