Vulnerability in Exim Mail Server Let Hackers Gain Root Access Remotely From 5 Million Email Servers

A Vulnerability resides in the Exim mail server allows both local and remote attacker to execute the arbitrary code and exploit the system to gain root access.

Exim is a mail transfer agent (MTA) developed by the University of Cambridge as an open-source project and is responsible for receiving, routing and delivering e-mail messages used on Unix-like operating systems. 

Last June, RCE Vulnerability in Millions of Exim Email Server, allowed attackers to Execute Arbitrary Command & Control the Server Remotely

Exit server that accepts the TLS connections are vulnerable to execute the malicious code remotely by an attacker, and it does not depend on the TLS library, so both GnuTLS and OpenSSL are vulnerable.

In order to exploit the vulnerability, the attacker sending a SNI ending in a backslash-null sequence during the initial TLS handshake.

The remote code execution vulnerability affected all Exim mail server versions up to 4.92.1, and the vulnerability has been fixed in the new version 4.92.2.

Qualys analyzed the vulnerability and released a PoC exploit code, also the vulnerability can be tracked as CVE-2019-15846 .

Based on Shodan report, more than 5 Million Exim server is running across the internet and many of them are still unpatched.

Since the vulnerability has been patched and releases the new version, the server administrator is recommended to apply the patch immediately before cybercriminals exploit the Exim server.

You can download and build a fixed version here and GitHub.

Also read about Penetration Testing Mail Server with Email Spoofing – Exploiting Open Relay configured Public Mail Servers.

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