CVE-2026-3621: IBM WebSphere Liberty Auth Bypass Flaw

CVE-2026-3621 Overview

IBM WebSphere Application Server - Liberty versions 17.0.0.3 through 26.0.0.4 is vulnerable to identity spoofing under limited conditions when an application is deployed without authentication and authorization configured. This vulnerability (CWE-269: Improper Privilege Management) allows attackers to potentially impersonate other users or system components when the target application lacks proper security controls.

Critical Impact

Identity spoofing vulnerability in IBM WebSphere Application Server Liberty could allow an attacker to impersonate legitimate users under specific deployment conditions where authentication and authorization are not properly configured.

Affected Products

• IBM WebSphere Application Server - Liberty 17.0.0.3 through 26.0.0.4

Discovery Timeline

• April 23, 2026 - CVE-2026-3621 published to NVD
• April 23, 2026 - Last updated in NVD database

Technical Details for CVE-2026-3621

Vulnerability Analysis

This identity spoofing vulnerability exists in IBM WebSphere Application Server Liberty when applications are deployed without proper authentication and authorization configurations. The flaw stems from improper privilege management (CWE-269), where the application server fails to adequately verify user identities under certain deployment scenarios.

The vulnerability requires network access and involves high attack complexity, meaning exploitation is not straightforward and requires specific conditions to be met. An attacker with low privileges could potentially exploit this flaw to gain unauthorized access to resources or impersonate other users, affecting the confidentiality, integrity, and availability of the target system.

Root Cause

The root cause of CVE-2026-3621 lies in improper privilege management within IBM WebSphere Application Server Liberty. When applications are deployed without explicitly configuring authentication and authorization mechanisms, the server may not properly validate user identities, creating conditions where identity spoofing becomes possible. This represents a security misconfiguration scenario where the absence of security controls exposes the application to identity-based attacks.

Attack Vector

The attack vector for this vulnerability is network-based, requiring the attacker to have network access to the vulnerable WebSphere Application Server Liberty instance. The exploitation path involves:

1. Identifying a Liberty server running a vulnerable version (17.0.0.3 through 26.0.0.4)
2. Locating an application deployed without authentication/authorization configured
3. Crafting requests that exploit the identity spoofing condition
4. Impersonating legitimate users to gain unauthorized access or perform privileged operations

The attack complexity is high, indicating that successful exploitation requires specific conditions beyond just network access, and the attacker needs low-level privileges to initiate the attack.

Detection Methods for CVE-2026-3621

Indicators of Compromise

• Unexpected authentication events or session creation without proper credential validation
• Anomalous user activity where actions are attributed to users who were not actively logged in
• Log entries showing access to protected resources by users who should not have permissions
• Unusual patterns in authentication logs indicating potential identity spoofing attempts

Detection Strategies

• Review WebSphere Application Server Liberty logs for authentication anomalies and unauthorized access patterns
• Monitor for applications deployed without security constraints in the server.xml configuration
• Implement security auditing to track identity verification events across deployed applications
• Use application security scanning tools to identify applications lacking authentication/authorization configurations

Monitoring Recommendations

• Enable detailed logging for authentication and authorization events in WebSphere Application Server Liberty
• Configure alerts for failed authentication attempts followed by successful access to protected resources
• Monitor network traffic to Liberty servers for suspicious request patterns
• Regularly audit deployed applications to ensure proper security configurations are in place

How to Mitigate CVE-2026-3621

Immediate Actions Required

• Review all deployed applications on IBM WebSphere Application Server Liberty for proper authentication and authorization configurations
• Apply the security patch from IBM as soon as available
• Implement network-level access controls to limit exposure of vulnerable servers
• Enable security auditing to detect potential exploitation attempts

Patch Information

IBM has released information regarding this vulnerability. Administrators should consult the IBM Support Document for detailed patch information and remediation guidance. Organizations should plan to upgrade to a patched version of IBM WebSphere Application Server Liberty as soon as possible.

Workarounds

• Ensure all deployed applications have authentication and authorization properly configured in server.xml
• Implement application-level security constraints for all web resources
• Use role-based access control to restrict access to sensitive functionality
• Deploy network segmentation to limit access to WebSphere Application Server Liberty instances

# Example security configuration in server.xml
<server>
    <featureManager>
        <feature>appSecurity-3.0</feature>
        <feature>servlet-4.0</feature>
    </featureManager>
    
    <basicRegistry id="basic" realm="BasicRealm">
        <user name="admin" password="securePassword"/>
    </basicRegistry>
    
    <webApplication location="myapp.war" contextRoot="/myapp">
        <application-bnd>
            <security-role name="AuthenticatedUser">
                <user name="admin"/>
            </security-role>
        </application-bnd>
    </webApplication>
</server>