Authorization Bypass in Cap-go via Limited API Keys

Executive Summary

CVE-2026-56310 is an authorization bypass vulnerability in Cap-go versions before 12.128.2. It affects the GET /organization/members endpoint, allowing API keys that are limited to specific organizations to bypass their restrictions. This means attackers with such org-limited API keys can access membership data from organizations outside their assigned scope.

• The exposed membership data includes user IDs (uid), email addresses, profile image URLs, roles, and temporary status flags.

The root cause is improper authorization enforcement where the endpoint fails to enforce the API key's organization scope after basic role-based access control (RBAC) checks.

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Impact Analysis

This vulnerability can lead to unauthorized disclosure of sensitive membership information from organizations that an attacker should not have access to.

• Attackers can read user identifiers, email addresses, profile images, roles, and temporary status flags of members in organizations outside their authorized scope.

Such unauthorized access can compromise privacy and potentially aid further attacks or social engineering by exposing internal organizational membership details.

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Mitigation Strategies

To mitigate this vulnerability, you should upgrade Cap-go to version 12.128.2 or later, where the authorization bypass issue in the GET /organization/members endpoint has been fixed.

Additionally, review and restrict the use of org-limited API keys to minimize exposure until the patch is applied.

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Detection Guidance

This vulnerability involves an authorization bypass in the GET /organization/members endpoint allowing org-limited API keys to access membership data outside their assigned organizations.

To detect exploitation attempts on your network or system, you can monitor and log requests to the GET /organization/members endpoint, especially those made using org-limited API keys.

Suggested commands to help detect potential exploitation include:

• Using network traffic analysis tools like tcpdump or Wireshark to filter HTTP GET requests to /organization/members.
• Example tcpdump command: tcpdump -i any -A 'tcp port 80 or tcp port 443' | grep 'GET /organization/members'
• Checking server access logs for unusual or unauthorized GET requests to /organization/members endpoint.
• Example grep command on server logs: grep 'GET /organization/members' /var/log/nginx/access.log
• Reviewing API key usage logs to identify org-limited keys accessing organizations outside their scope.

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Compliance Impact

This vulnerability allows attackers with org-limited API keys to bypass restrictions and access sensitive membership data such as user IDs, email addresses, profile images, roles, and temporary status flags from organizations outside their assigned scope.

Unauthorized access to such personal and organizational data could lead to non-compliance with data protection regulations like GDPR and HIPAA, which require strict controls on access to personal and sensitive information.

By exposing membership data beyond authorized boundaries, the vulnerability increases the risk of data breaches and unauthorized disclosure, potentially violating privacy and security requirements mandated by these standards.

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