Understanding CVE-2024-21762: a critical vulnerability in Fortinet’s FortiOS

What is CVE-2024-21762?

CVE-2024-21762 is identified as a critical vulnerability within the SSL VPN functionality of Fortinet’s FortiOS. It’s classified as an out-of-bound write vulnerability. In simpler terms, it’s akin to a hidden flaw in a network’s security system, potentially allowing unauthorised external access. The seriousness of this vulnerability is underscored by its high CVSS score of 9.6 to 9.8, indicating a significant risk level. Reports suggest that this vulnerability could already be exploited in the wild, though specific details of such exploitations remain sparse as of now.

Impact and severity?

The impact of CVE-2024-21762 is broad, affecting multiple versions of FortiOS. The vulnerability, if exploited, could enable external actors to execute commands or access systems without proper authorization. This could potentially lead to sensitive data exposure or disruption in network operations. It’s crucial for organisations using affected versions of FortiOS to take immediate actions to patch their systems.

Mitigation and patch availability?

Fortinet has released updates to address this critical vulnerability in their FortiOS operating system. The vulnerability, as mentioned earlier, affects the SSL VPN functionality of FortiOS. To mitigate this vulnerability, Fortinet recommends updating the affected FortiOS versions to the latest releases. Specifically, users should upgrade to the following versions or above, depending on their current version:

• FortiOS 7.4: Upgrade to 7.4.3 or above
• FortiOS 7.2: Upgrade to 7.2.7 or above
• FortiOS 7.0: Upgrade to 7.0.14 or above
• FortiOS 6.4: Upgrade to 6.4.15 or above
• FortiOS 6.2: Upgrade to 6.2.16 or above

For those using FortiOS 6.0, which is also affected, the recommendation is to migrate to a fixed release version as FortiOS 6.0 versions are all impacted. Applying these updates is crucial for protecting the network from potential exploitation through this vulnerability. In cases where immediate patching is not possible, Fortinet advises disabling the SSL VPN feature as a temporary security measure.

Broader context: Zero-day vulnerabilities and cybersecurity threat landscape

CVE-2024-21762 is a stark reminder of the persistent threat posed by zero-day vulnerabilities in the cybersecurity landscape. Zero-day exploits, which are vulnerabilities exploited before a vendor has issued a patch, represent about 3% of all cyber threats according to IBM. However, the potential impact of these exploits can be significant, particularly when they target widely-used software. The rapid increase in devices and systems connected to the internet, including cloud hosting, mobile, and IoT technologies, has led to a surge in software flaws and consequently, the number of zero-day exploits. In 2021, there were 80 zero-days exploited in the wild, more than double the previous record volume in 2019.