CVE-2021-24020 : What You Need to Know

A missing cryptographic step in the implementation of the hash digest algorithm in FortiMail 6.4.0 through 6.4.4, and 6.2.0 through 6.2.7 may allow an unauthenticated attacker to tamper with signed URLs by appending further data which allows bypass of signature verification.

Understanding CVE-2021-24020

This CVE identifies a vulnerability in Fortinet FortiMail versions 6.4.0 through 6.4.4, and 6.2.0 through 6.2.7 that could be exploited by an attacker to manipulate signed URLs, potentially leading to bypass of signature verification.

What is CVE-2021-24020?

The vulnerability in the hash digest algorithm implementation in FortiMail versions 6.4.0 through 6.4.4, and 6.2.0 through 6.2.7 allows an attacker to modify signed URLs by adding data, enabling them to bypass the verification of digital signatures.

The Impact of CVE-2021-24020

With a CVSS base score of 7.5 (High severity), this CVE poses a significant threat. An unauthenticated attacker could exploit this vulnerability through a network attack, potentially compromising the confidentiality, integrity, and availability of affected systems.

Technical Details of CVE-2021-24020

This section delves deeper into the technical aspects of the vulnerability.

Vulnerability Description

The missing cryptographic step in the hash digest algorithm implementation could be leveraged by attackers to tamper with signed URLs, enabling them to bypass signature verification.

Affected Systems and Versions

FortiMail versions 6.4.0 through 6.4.4, and 6.2.0 through 6.2.7 are confirmed to be affected by this vulnerability.

Exploitation Mechanism

Attackers can exploit this vulnerability by appending additional data to signed URLs, manipulating the signature verification process, and potentially gaining unauthorized access.

Mitigation and Prevention

To safeguard affected systems, immediate actions and long-term security practices are essential.

Immediate Steps to Take

Organizations should consider implementing network controls, monitoring for suspicious activity, and restricting access to potentially vulnerable systems.

Long-Term Security Practices

Regular security assessments, patch management, and employee training on identifying phishing attempts can enhance overall security posture.

Patching and Updates

Vendor-issued patches should be promptly applied to FortiMail versions 6.4.0 through 6.4.4, and 6.2.0 through 6.2.7 to mitigate the risk associated with this vulnerability.