Authorization Bypass in SCIM Endpoint via Username Collision

Executive Summary

This vulnerability involves improper authorization validation in the SCIM endpoint for federated users. When a local and federated user share the same username, a malicious federated user can perform arbitrary operations on local user accounts via SCIM 2.0 or SCIM 1.1 endpoints. This could lead to user account takeover, especially in deployments supporting user self-registration.

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Detection Guidance

Check WSO2 Identity Server logs for SCIM endpoint access attempts, especially when local and federated users share the same username. Monitor for unauthorized operations on user accounts via SCIM 1.1 or SCIM 2.0 endpoints. Review authentication logs for federated user sessions performing actions outside expected scope.

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Impact Analysis

Affected users may experience unauthorized access to local user accounts, leading to potential account takeover. Attackers could manipulate user data, escalate privileges, or perform actions as the compromised user. Systems without user self-registration face reduced but still significant risk.

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Compliance Impact

This vulnerability could lead to unauthorized access to sensitive user data, violating confidentiality requirements in GDPR and HIPAA. Compliance may be impacted due to potential data breaches, unauthorized modifications, or loss of user control over personal information.

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Mitigation Strategies

Apply available patches from WSO2 GitHub pull requests or update to the latest unaffected versions. Disable user self-registration if supported. Review and restrict SCIM endpoint access to trusted sources. Monitor for suspicious activity and enforce unique usernames across local and federated users.

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