CVE-2021-24012 : Vulnerability Insights and Analysis

This article provides an overview of CVE-2021-24012, a vulnerability found in Fortinet FortiOS versions 6.4.0 to 6.4.4 that could allow an LDAP user to connect to SSLVPN using any certificate signed by a trusted Certificate Authority.

Understanding CVE-2021-24012

CVE-2021-24012 is related to an improper following of a certificate's chain of trust vulnerability in FortiGate versions 6.4.0 to 6.4.4, potentially enabling unauthorized LDAP users to access SSLVPN with certificates signed by trusted CAs.

What is CVE-2021-24012?

CVE-2021-24012 is a medium-severity vulnerability that arises from the incorrect verification of certificate chains in Fortinet FortiOS, allowing LDAP users to authenticate SSLVPN with certificates from trusted CAs, irrespective of the actual user rights.

The Impact of CVE-2021-24012

The vulnerability's impact is medium severity, with a CVSS base score of 6.4 (Medium). If exploited, it could permit unauthorized access and compromise the SSLVPN's integrity, although the confidentiality and availability impacts are considered low.

Technical Details of CVE-2021-24012

This section covers in-depth technical aspects of the CVE-2021-24012 vulnerability.

Vulnerability Description

The vulnerability arises in Fortinet FortiOS 6.4.0 to 6.4.4 due to improper handling of certificate chain validation, enabling LDAP users to bypass authentication restrictions and establish connections to SSLVPN using certificates signed by trusted CAs.

Affected Systems and Versions

Fortinet FortiOS versions 6.4.0 to 6.4.4 are affected by this vulnerability. Users with these versions are at risk of LDAP users exploiting insecure certificate validation to gain unauthorized SSLVPN access.

Exploitation Mechanism

LDAP users can exploit the vulnerability by presenting a certificate signed by a trusted CA, bypassing the expected validation process, and gaining unauthorized access to SSLVPN.

Mitigation and Prevention

To address CVE-2021-24012, immediate actions and long-term security practices are recommended to mitigate the risk of exploitation and enhance overall system security.

Immediate Steps to Take

It is crucial to apply security patches and updates provided by Fortinet to remediate CVE-2021-24012. Additionally, monitoring SSLVPN connections and auditing user access can help detect and prevent unauthorized activities.

Long-Term Security Practices

Implementing strong certificate verification mechanisms, enforcing least privilege access controls, and regularly updating security configurations can enhance the overall security posture and prevent similar vulnerabilities in the future.

Patching and Updates

Fortinet has released patches addressing the vulnerability in FortiOS versions 6.4.0 to 6.4.4. Users are strongly advised to apply these patches promptly to eliminate the risk of LDAP users exploiting the certificate chain trust vulnerability.