CVE-2019-16928 : Security Advisory and Response

Exim versions 4.92 to 4.92.2 are vulnerable to remote code execution due to a heap-based buffer overflow in the string_vformat function within string.c.

Understanding CVE-2019-16928

This CVE involves a distinct vulnerability from CVE-2019-15846, allowing remote code execution in Exim versions 4.92 to 4.92.2.

What is CVE-2019-16928?

CVE-2019-16928 is a heap-based buffer overflow vulnerability in Exim versions 4.92 to 4.92.2, specifically related to an extended HELO command.

The Impact of CVE-2019-16928

The vulnerability allows remote attackers to execute arbitrary code on the target system, potentially leading to a complete compromise of the affected system.

Technical Details of CVE-2019-16928

Exim 4.92 through 4.92.2 is susceptible to remote code execution due to a heap-based buffer overflow in the string_vformat function within string.c.

Vulnerability Description

A heap-based buffer overflow occurs in the string_vformat function within string.c, triggered by a long EHLO command.

Affected Systems and Versions

Exim versions 4.92 to 4.92.2

Exploitation Mechanism

The vulnerability can be exploited by sending a specially crafted EHLO command to the Exim server, leading to the execution of malicious code.

Mitigation and Prevention

It is crucial to take immediate steps to secure systems and prevent exploitation of CVE-2019-16928.

Immediate Steps to Take

Update Exim to a non-vulnerable version immediately.
Implement network-level controls to restrict access to the Exim server.
Monitor for any unusual EHLO commands or system behavior.

Long-Term Security Practices

Regularly update Exim and other software to patch known vulnerabilities.
Conduct security assessments and penetration testing to identify and address potential weaknesses.
Educate system administrators and users on best security practices.

Patching and Updates

Apply the latest security patches provided by Exim to address the CVE-2019-16928 vulnerability.