CVE-2021-24018 : Security Advisory and Response

A buffer underwrite vulnerability in the firmware verification routine of Fortinet FortiOS before 7.0.1 may allow an attacker to execute arbitrary code via a crafted firmware image.

Understanding CVE-2021-24018

This CVE describes a buffer underwrite vulnerability in Fortinet FortiOS before version 7.0.1, which could be exploited by an attacker in an adjacent network to potentially execute arbitrary code.

What is CVE-2021-24018?

CVE-2021-24018 is a security flaw in the firmware verification routine of Fortinet FortiOS, allowing attackers in the adjacent network to run code through a tailored firmware image.

The Impact of CVE-2021-24018

The impact of this vulnerability is rated as Medium severity with a CVSS base score of 4.3. An attacker with high privileges in the adjacent network can exploit this flaw to execute unauthorized code.

Technical Details of CVE-2021-24018

This section provides more insight into the vulnerability, the affected systems, and how the exploitation can occur.

Vulnerability Description

The vulnerability exists in the firmware verification routine of FortiOS before version 7.0.1, enabling attackers to perform a buffer underwrite attack by leveraging a specifically crafted firmware image.

Affected Systems and Versions

Fortinet FortiOS versions before 7.0.1 are affected by this vulnerability. Users with these versions should take immediate action to mitigate the risk.

Exploitation Mechanism

An attacker positioned in the adjacent network can exploit this vulnerability by sending a specially designed firmware image to the target system, triggering the buffer underwrite and leading to arbitrary code execution.

Mitigation and Prevention

To prevent exploitation and secure the system against potential threats associated with CVE-2021-24018, users should take the following steps:

Immediate Steps to Take

Upgrade Fortinet FortiOS to version 7.0.1 or later to eliminate the vulnerability.
Monitor network traffic for any suspicious activities that might indicate an exploit attempt.

Long-Term Security Practices

Regularly update and patch Fortinet FortiOS to protect against known vulnerabilities.
Implement network segmentation to limit the impact of intrusions from adjacent networks.

Patching and Updates

Stay informed about security advisories and updates from Fortinet to promptly apply patches and protect the system from emerging threats.