CVE-2021-21043 : Security Advisory and Response

This article provides an overview of CVE-2021-21043, a Reflected Cross-site Scripting (XSS) vulnerability affecting Adobe Experience Manager (AEM) versions 4.9.2 and earlier.

Understanding CVE-2021-21043

CVE-2021-21043 is a security vulnerability identified in Adobe Experience Manager (AEM) that allows attackers to inject malicious JavaScript code into vulnerable form fields through the version-compare and page-compare tools.

What is CVE-2021-21043?

The vulnerability arises from improper handling of invalid JCR characters in ACS Commons version 4.9.2 and earlier. By exploiting this flaw, threat actors can execute arbitrary code within a victim's browser by tricking users into interacting with specially crafted content.

The Impact of CVE-2021-21043

With a CVSS base score of 6.1 (Medium severity), this XSS vulnerability poses a moderate risk. Although no direct impact on data confidentiality or integrity is reported, successful exploitation could lead to unauthorized code execution in the victim's browser.

Technical Details of CVE-2021-21043

This section delves into the technical aspects of the vulnerability, including its description, affected systems, and the exploitation mechanism.

Vulnerability Description

The vulnerability allows attackers to inject and execute malicious JavaScript code in the victim's browser through vulnerable form fields associated with the version-compare and page-compare tools in ACS Commons.

Affected Systems and Versions

Adobe Experience Manager (AEM) versions 4.9.2 and earlier are confirmed to be impacted by this XSS vulnerability due to improper handling of JCR characters in ACS Commons.

Exploitation Mechanism

To exploit CVE-2021-21043, attackers need to craft malicious content and persuade users to interact with it. By injecting specially coded inputs into vulnerable form fields, threat actors can execute arbitrary JavaScript code within the victim's browser.

Mitigation and Prevention

In response to CVE-2021-21043, it is crucial for organizations to take immediate steps to mitigate the risk and implement long-term security measures.

Immediate Steps to Take

Update ACS Commons to a non-vulnerable version or apply relevant patches provided by Adobe.
Educate users about the risks of interacting with untrusted content to prevent XSS attacks.

Long-Term Security Practices

Regularly monitor security advisories from Adobe and apply patches promptly.
Conduct security assessments to identify and remediate vulnerabilities in Adobe Experience Manager installations.

Patching and Updates

Adobe has released patches to address the XSS vulnerability in ACS Commons. Ensure all affected systems are updated to the latest non-vulnerable versions to prevent exploitation.