CVE-2026-56239 in Capgo
Summary
by MITRE • 06/21/2026
Capgo before 12.128.2 contains a potential privilege escalation vulnerability in the public.apply_usage_overage SECURITY DEFINER function, which performs sensitive billing operations without enforcing internal authorization checks (no validation of auth.uid(), org membership, or check_min_rights). Because the function runs with the owner's privileges, it bypasses Row Level Security. If EXECUTE permission is available to the authenticated or anon roles (explicitly or via default privileges), an authenticated user could invoke it via Supabase RPC to manipulate billing data for arbitrary organizations, including unauthorized credit depletion and fraudulent overage event insertion.
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Analysis
by VulDB Data Team • 06/21/2026
The vulnerability in Capgo versions prior to 12.128.2 represents a critical privilege escalation flaw within the Supabase-based backend architecture that fundamentally undermines the application's security model. This issue resides in the public.apply_usage_overage function which operates under a SECURITY DEFINER context, meaning it executes with the privileges of the function's owner rather than the caller. The function's design lacks essential authorization controls that should validate whether the calling user possesses legitimate rights to perform billing operations. The absence of auth.uid() validation means the system cannot verify that the requesting user is authenticated, while the lack of organization membership checks removes the essential boundary that should prevent users from accessing resources they don't belong to. Additionally, the function fails to implement check_min_rights validation which would normally enforce minimum permission levels required for such sensitive operations.
The operational impact of this vulnerability extends far beyond simple unauthorized access, as it enables attackers to manipulate billing data for any organization within the system. When the EXECUTE permission is granted to authenticated or anonymous roles either explicitly through direct grants or implicitly via default privileges, the vulnerability becomes exploitable by any user who can reach the Supabase RPC endpoint. The function's ability to bypass Row Level Security mechanisms means that even if the system has proper access controls configured at the table level, the SECURITY DEFINER function can circumvent these protections entirely. This creates a dangerous attack surface where an authenticated user could potentially deplete credits from organizations they have no legitimate access to, insert fraudulent overage events, and manipulate billing records in ways that could result in significant financial loss for affected customers.
The technical implementation of this vulnerability aligns with common patterns found in database security misconfigurations that map to CWE-276, which deals with incorrect permissions for critical resources. The flaw demonstrates poor principle of least privilege enforcement and represents a classic case of insufficient authorization checking within database functions. From an ATT&CK perspective, this vulnerability maps to T1078 Valid Accounts and T1484 Defense Evasion, as attackers could leverage legitimate user accounts to perform unauthorized billing operations while potentially avoiding detection mechanisms that rely on normal access patterns. The vulnerability also relates to T1566 Impersonation, since the function's SECURITY DEFINER nature allows attackers to effectively impersonate system-level privileges within the billing context.
Mitigation strategies should focus on implementing comprehensive authorization checks within the function, including explicit validation of auth.uid() to ensure proper authentication, verification of organization membership through database joins or lookup tables, and enforcement of minimum rights requirements before allowing billing operations to proceed. The function's SECURITY DEFINER context should be carefully reviewed and potentially restructured to use INVOKER DEFINER if the function doesn't require elevated privileges, or alternatively, the function should be redesigned to properly validate all inputs and enforce appropriate access controls. Additionally, administrators should audit and restrict EXECUTE permissions on the function to only those roles that absolutely require such access, and implement monitoring for unusual billing operations that could indicate exploitation attempts. The fix should also include implementing proper logging and alerting mechanisms to detect unauthorized access attempts to billing functions and ensure that all privilege escalation attempts are properly audited and reported.