Authorization Bypass in Capgo Channel Creation

Executive Summary

This vulnerability exists in Capgo versions before 12.128.2 and involves an authorization bypass in the channel creation endpoint.

Authenticated users who have the app.create_channel permission can exploit a logic mismatch between the validation that checks if a channel exists and the operation that creates or updates channels.

By reusing existing channel names, attackers can overwrite existing channels, reassign channel ownership, and modify important production channel configurations.

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Detection Guidance

Detection of this vulnerability involves monitoring for unauthorized channel overwrite attempts via the POST /channel endpoint, especially by users with the app.create_channel permission.

Since the vulnerability exploits a logic mismatch in the channel creation endpoint allowing reuse of existing channel names, you can audit logs for POST requests to /channel where the channel name already exists but ownership changes.

Commands to detect such activity would depend on your logging and monitoring setup, but examples include searching application logs or API gateway logs for suspicious POST /channel requests with repeated channel names or ownership changes.

• Use grep or similar tools to search logs for POST /channel requests: grep 'POST /channel' /path/to/logfile
• Filter logs for repeated channel names being created or updated by different users.
• Monitor for changes in channel ownership fields in your database or audit logs.

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Impact Analysis

This vulnerability can lead to unauthorized modification of critical production channels.

Attackers with certain permissions can overwrite existing channels, potentially disrupting communication or operations.

It can result in loss of integrity and availability of channel configurations, which may impact business processes relying on these channels.

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Compliance Impact

The vulnerability allows attackers with certain permissions to overwrite existing channels and reassign ownership, enabling unauthorized changes to critical production configurations. This improper authorization and potential unauthorized access could lead to violations of compliance requirements related to data integrity, access control, and auditability under standards such as GDPR and HIPAA.

Specifically, unauthorized modification of production channels may compromise system integrity and confidentiality, which are key aspects of regulatory frameworks that mandate strict access controls and protection of sensitive data.

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Mitigation Strategies

Immediate mitigation steps include updating Capgo to version 12.128.2 or later where the vulnerability is fixed.

If an immediate update is not possible, restrict or audit users with the app.create_channel permission to prevent unauthorized channel creation or modification.

Implement additional authorization checks on the channel creation endpoint to ensure ownership cannot be overwritten by reusing channel names.

Review and align existence validation logic with upsert operations to prevent bypassing ownership constraints.

Prevent modification of the created_by field after channel creation to maintain ownership integrity.

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