CVE-2021-42770 : What You Need to Know

A Cross-site scripting (XSS) vulnerability was discovered in OPNsense before 21.7.4 via the LDAP attribute return in the authentication tester.

Understanding CVE-2021-42770

What is CVE-2021-42770?

CVE-2021-42770 is a Cross-site scripting (XSS) vulnerability found in OPNsense before version 21.7.4. It specifically affects the LDAP attribute return in the authentication tester.

The Impact of CVE-2021-42770

The vulnerability allows attackers to inject malicious scripts into web pages viewed by other users, potentially leading to unauthorized access, session hijacking, or defacement of websites.

Technical Details of CVE-2021-42770

Vulnerability Description

The vulnerability arises from inadequate input validation in the LDAP attribute return of OPNsense, enabling the execution of XSS attacks.

Affected Systems and Versions

Product: OPNsense
Versions affected: Before 21.7.4

Exploitation Mechanism

Attackers exploit this vulnerability by injecting malicious scripts into the LDAP attribute return field of the authentication tester in OPNsense.

Mitigation and Prevention

Immediate Steps to Take

Update OPNsense to version 21.7.4 or later to mitigate the vulnerability.
Regularly monitor and review LDAP attribute return inputs for any suspicious or unexpected content.

Long-Term Security Practices

Implement strict input validation procedures to prevent XSS attacks in web applications.
Educate developers and users about the risks of XSS vulnerabilities and appropriate mitigation strategies.

Patching and Updates

Apply security patches and updates provided by OPNsense promptly to address known vulnerabilities.