CVE-2021-3539 : Exploit Details and Defense Strategies

EspoCRM 6.1.6 and prior versions are affected by a persistent cross-site scripting (XSS) vulnerability related to user-supplied avatar images. This vulnerability allows attackers to inject malicious scripts, posing a risk to user confidentiality.

Understanding CVE-2021-3539

This CVE refers to a persistent XSS vulnerability in EspoCRM, affecting versions up to 6.1.6. The issue was discovered by Wiktor Sędkowski of Nokia and Trevor Christiansen of Rapid7 through Rapid7's vulnerability disclosure program.

What is CVE-2021-3539?

CVE-2021-3539 is a type II persistent XSS vulnerability in EspoCRM, allowing attackers to execute malicious scripts via user-supplied avatar images.

The Impact of CVE-2021-3539

The vulnerability can result in high confidentiality impact, low integrity impact, and requires low privileges for exploitation. With a CVSS base score of 6.3, it poses a medium severity threat.

Technical Details of CVE-2021-3539

This section covers details about the vulnerability such as its description, affected systems, and the exploitation mechanism.

Vulnerability Description

EspoCRM versions up to 6.1.6 are susceptible to a persistent XSS flaw in how the application processes user-provided avatar images.

Affected Systems and Versions

The vulnerability affects EspoCRM versions up to 6.1.6. Users using these versions are at risk of exploitation.

Exploitation Mechanism

Attackers can exploit this vulnerability by uploading specially crafted avatar images containing malicious scripts, which can then be executed within the application.

Mitigation and Prevention

To address CVE-2021-3539, users and administrators should take immediate steps, implement long-term security practices, and apply relevant patches and updates.

Immediate Steps to Take

Users should update their EspoCRM installations to version 6.1.7 or later to mitigate the risk of exploitation from this vulnerability.

Long-Term Security Practices

It is recommended to regularly update software, educate users about phishing attacks, and sanitize user inputs to prevent XSS vulnerabilities.

Patching and Updates

EspoCRM addressed this vulnerability in version 6.1.7. Users are advised to promptly patch their installations to protect against potential attacks.