CVE-2021-39038: IBM WebSphere Application Server CSRF Flaw

CVE-2021-39038 Overview

IBM WebSphere Application Server 9.0 and IBM WebSphere Application Server Liberty 17.0.0.3 through 22.0.0.2 are vulnerable to a clickjacking attack that could allow a remote attacker to hijack the clicking action of the victim. By persuading a victim to visit a malicious web site, a remote attacker could exploit this vulnerability to hijack the victim's click actions and possibly launch further attacks against the victim. This vulnerability is tracked as IBM X-Force ID: 213968.

Critical Impact

Successful exploitation allows attackers to trick authenticated users into performing unintended actions on WebSphere Application Server administrative interfaces, potentially leading to unauthorized configuration changes or data exposure.

Affected Products

• IBM WebSphere Application Server 9.0
• IBM WebSphere Application Server Liberty 17.0.0.3 through 22.0.0.2

Discovery Timeline

• 2022-02-24 - CVE CVE-2021-39038 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2021-39038

Vulnerability Analysis

This vulnerability falls under CWE-1021 (Improper Restriction of Rendered UI Layers or Frames), commonly known as clickjacking or UI redressing. The affected IBM WebSphere Application Server versions fail to properly implement frame-busting protections, allowing malicious websites to embed the application's pages within hidden or disguised iframe elements.

When a user visits an attacker-controlled website, the malicious page can load the vulnerable WebSphere interface in an invisible iframe positioned over seemingly innocuous UI elements. As the victim interacts with what appears to be the malicious site, their clicks are actually directed to the underlying WebSphere application, executing actions without the user's knowledge or consent.

Root Cause

The root cause of this vulnerability is the improper restriction of rendered UI layers or frames in IBM WebSphere Application Server. The application does not adequately implement security headers such as X-Frame-Options or Content-Security-Policy frame-ancestors directives that would prevent the application from being embedded in frames on untrusted domains.

Attack Vector

The attack requires network access and some level of user interaction. An attacker must craft a malicious website that embeds the vulnerable WebSphere Application Server pages within invisible or disguised iframes. The attacker then persuades authenticated users to visit this malicious site through phishing emails, social engineering, or compromised websites.

Once on the malicious page, the victim's clicks are intercepted and redirected to perform unintended actions on the WebSphere application, such as modifying configurations, changing user permissions, or accessing sensitive administrative functions while believing they are interacting with benign content.

Detection Methods for CVE-2021-39038

Indicators of Compromise

• Unexpected administrative changes to WebSphere Application Server configurations with no corresponding audit trail from legitimate sessions
• User reports of being redirected to unfamiliar websites before experiencing unusual account behavior
• Web server logs showing referrer headers from external, untrusted domains when accessing administrative interfaces

Detection Strategies

• Monitor HTTP referrer headers for administrative requests originating from external or unknown domains
• Implement browser-based security monitoring to detect iframe embedding attempts from untrusted sources
• Review WebSphere access logs for patterns indicating automated or scripted interactions that may indicate clickjacking exploitation

Monitoring Recommendations

• Enable detailed audit logging for all administrative actions in WebSphere Application Server
• Deploy web application firewalls (WAF) configured to detect and block potential clickjacking attempts
• Implement user and entity behavior analytics (UEBA) to identify anomalous administrative activity patterns

How to Mitigate CVE-2021-39038

Immediate Actions Required

• Apply the security patch referenced in IBM Support Advisory #6559044 immediately
• Verify that X-Frame-Options headers are properly configured with DENY or SAMEORIGIN values on all administrative interfaces
• Implement Content Security Policy (CSP) headers with appropriate frame-ancestors directives to restrict framing to trusted domains only

Patch Information

IBM has released security updates to address this vulnerability. Administrators should consult the IBM Support Advisory #6559044 for detailed patch information and upgrade instructions. The fix is available for IBM WebSphere Application Server 9.0 and IBM WebSphere Application Server Liberty versions affected by this vulnerability. Additional technical details can be found in the IBM X-Force Vulnerability #213968.

Workarounds

• Configure reverse proxy or load balancer to inject X-Frame-Options: DENY headers for all responses from WebSphere Application Server
• Implement Content Security Policy headers at the web server level with frame-ancestors 'self' to prevent framing from external domains
• Restrict access to administrative interfaces to internal networks only through network segmentation and firewall rules
• Educate users about phishing risks and the importance of accessing WebSphere administrative consoles only through trusted bookmarks

# Example Apache configuration to add X-Frame-Options header
# Add to httpd.conf or appropriate virtual host configuration
Header always set X-Frame-Options "SAMEORIGIN"
Header always set Content-Security-Policy "frame-ancestors 'self'"