Compliance Impact

This vulnerability allows attackers to bypass enforced hashed API key restrictions and gain unauthorized access to protected resources by sending plaintext API keys directly to the PostgREST/RLS plane. Such unauthorized access can lead to exposure or misuse of sensitive data.

Because the vulnerability undermines authentication controls and allows unauthorized access, it can negatively impact compliance with common standards and regulations like GDPR and HIPAA, which require strict access controls and protection of sensitive data.

Organizations relying on Capgo versions before 12.128.2 may be at risk of non-compliance if this vulnerability is exploited, as it compromises the integrity of security controls designed to protect data privacy and confidentiality.

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Executive Summary

CVE-2026-56243 is a high-severity authentication bypass vulnerability in Capgo versions before 12.128.2. It occurs because the PostgREST/RLS plane accepts plaintext API keys through the "capgkey" header even when the system is configured to enforce hashed API keys.

This means that attackers can bypass the organization's hashed-key enforcement by sending plaintext API keys directly to the PostgREST/RLS plane, gaining unauthorized access to protected resources.

The root cause is a policy split where the backend API rejects plaintext keys correctly, but the PostgREST/RLS plane still authorizes access using plaintext keys, defeating the intended security control.

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Impact Analysis

This vulnerability allows attackers to bypass security controls that enforce hashed API keys, enabling unauthorized access to protected resources.

As a result, sensitive data or functionality protected by these API keys could be exposed or manipulated by unauthorized users.

Administrators may mistakenly believe that legacy plaintext API keys are no longer usable, while attackers can exploit this flaw to gain access.

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Detection Guidance

This vulnerability involves the acceptance of plaintext API keys via the "capgkey" header in the PostgREST/RLS plane despite hashed API key enforcement being enabled. To detect this on your network or system, you can monitor API requests for the presence of the "capgkey" header carrying plaintext API keys.

Commands to detect this might include inspecting HTTP request headers in your logs or using network traffic analysis tools to filter for requests containing the "capgkey" header with plaintext keys.

• Use tools like tcpdump or Wireshark to capture network traffic and filter for HTTP headers named "capgkey".
• Search your API server logs for entries containing the "capgkey" header with non-hashed (plaintext) API keys.
• Example command to search logs: grep -i 'capgkey:' /path/to/api/logs
• Example tcpdump filter: tcpdump -A -s 0 'tcp port 80 or tcp port 443' | grep -i 'capgkey:'

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Mitigation Strategies

The immediate mitigation step is to upgrade Capgo to version 12.128.2 or later, where the vulnerability has been patched.

Additionally, ensure that the org-level hashed-key enforcement is consistently applied in the PostgREST/RLS identity path to prevent acceptance of plaintext API keys.

• Apply the official patch or upgrade to Capgo version 12.128.2 or newer.
• Review and enforce configuration settings to ensure that plaintext API keys are rejected in all API planes, including PostgREST/RLS.
• Audit API usage to identify and revoke any plaintext API keys that may have been used.

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