A recent security advisory has highlighted a Stack-based Buffer Overflow Vulnerability (CWE-121) in Fortinet FortiOS before 7..3, which could potentially allow an attacker with correct authorization levels to execute arbitrary code on the target system. This vulnerability (CVE-2023-29182) has implications for both security and system administrators managing networks under Fortinet FortiOS. In this post, we will provide an in-depth look at the vulnerability, underlying exploitable condition, and the potential exploitation method.
The Vulnerability, CVE-2023-29182, involves a stack-based buffer overflow in Fortinet FortiOS before 7..3 that occurs due to improper input validation in parsing CLI commands. Specifically, the input submitted by the malicious user exceeds the allocated buffer size resulting in an overflow condition.
Fortinet has acknowledged the vulnerability, and you can check out the original advisory on their website here.
In order to exploit this vulnerability, the attacker must have sufficient privileges to bypass built-in security measures in Fortinet FortiOS. This means that the attacker should be an authenticated user with specific administrative permissions on the target system. An anonymous or guest user cannot exploit this vulnerability.
The exploit essentially involves an attacker sending specially crafted CLI commands to the vulnerable Fortinet FortiOS device. The commands are malformed in such a way that it triggers the buffer overflow condition, potentially overwriting critical memory areas, and ultimately achieving arbitrary code execution.
An example of the exploit payload would look like (Note: This is a simplified representation and not the actual exploit):
_OVERFLOW_BUFFER_ = ""
exploit_payload = "CMD" + "\xa" + _OVERFLOW_BUFFER_ * 100
In the above code snippet, the _OVERFLOW_BUFFER_ string is repeated multiple times (100 in this example) to trigger an overflow of the allocated buffer size. The string "CMD" is meant to simulate a CLI command being sent to the Fortinet FortiOS. The linefeed character, \xa, is used to emulate the command separator.
Fortinet has already released a patch for this vulnerability, which has been fixed in FortiOS 7..3. Therefore, users are strongly encouraged to update their systems to the latest patched version.
To update your system, follow the official upgrade guide provided by Fortinet available here.
Although this particular vulnerability requires a privileged attacker to exploit, it serves as a strong reminder of the importance of keeping your systems up-to-date and properly monitored. System administrators should be diligent in ensuring that security patches are applied promptly.
With a better understanding of this CVE-2023-29182 stack-based buffer overflow vulnerability, Fortinet FortiOS users can take the necessary steps to protect their networks. Regularly reviewing security advisories, following best practices, and timely patching are all essential in maintaining a secure system environment.
Published on: 08/17/2023 10:15:00 UTC
Last modified on: 08/23/2023 15:36:00 UTC