CVE-2026-100627 in capgo.app
Summary
by MITRE • 09/26/2026
Capgo (Cap-go/capgo.app) server backend Supabase functions contain an incorrect authorization flaw in the API-key bundle promotion path. The PUT /bundle endpoint, available to "all" and "write" API keys, dispatches to setChannel, which authorizes with checkPermission(c, 'channel.promote_bundle', { appId: body.app_id }) and omits the request's channel_id. Because the omitted scope field is passed to rbac_check_permission_direct as SQL NULL, and channel-scope override evaluation is gated on p_channel_id IS NOT NULL, per-channel allow/deny overrides are never evaluated. A principal holding app-level channel.promote_bundle (granted by default to the app_developer and app_uploader roles) can therefore promote a bundle to a channel for which an explicit per-channel deny override exists, updating public.channels.version for the supplied channel_id; the target channel is only validated after authorization. The issue is confirmed on main at commit de66fa51e7ff2f50283cc1455c3d80ab3eb0ae43 and likely earlier versions; no patched version is known at the time of publication.
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Analysis
by VulDB Data Team • 09/26/2026
The vulnerability identified in Capgo server backend Supabase functions represents a critical broken access control flaw within the API-key bundle promotion mechanism. Specifically, the PUT /bundle endpoint, which accepts requests from principals possessing "all" or "write" level API keys, fails to enforce channel-specific authorization constraints during the bundle promotion process. The core technical error lies in how the application handles scope validation for per-channel permissions. When a request is processed, the system dispatches to a function named setChannel that attempts to authorize the action using checkPermission with the permission type 'channel.promote_bundle'. Crucially, this authorization call omits the channel_id from the context object passed to the underlying role-based access control evaluation logic.
This omission has significant technical consequences due to how the backend handles missing scope data. The omitted scope field is transmitted as SQL NULL to the rbac_check_permission_direct function. Within the database layer, the evaluation of per-channel allow or deny overrides is explicitly gated by a condition checking if p_channel_id IS NOT NULL. Because the channel identifier is nullified in this specific authorization path, the system bypasses any granular permission checks that might restrict bundle promotion for particular channels. Consequently, the application proceeds with the operation based solely on app-level permissions rather than evaluating whether the specific target channel permits such actions.
The operational impact of this flaw allows a principal holding app-level channel.promote_bundle privileges to promote bundles to any channel associated with their application, regardless of explicit per-channel deny overrides configured by administrators or other authorized users. This privilege is granted by default to roles such as app_developer and app_uploader, meaning that standard developers within an organization can inadvertently bypass security policies designed to restrict deployment targets. The target channel is only validated after the authorization check has already passed, allowing unauthorized updates to public.channels.version for the supplied channel_id. This undermines the integrity of release management processes and could lead to unintended deployments or policy violations across different project segments managed under a single application ID.
From an industry standard perspective, this vulnerability aligns with CWE-284 Improper Access Control, as it involves insufficient verification of proper authorization before granting access to resources. Furthermore, it maps to MITRE ATT&CK technique T1078 Valid Accounts, where attackers or malicious insiders leverage legitimate credentials and roles to perform actions that exceed their intended scope within specific contexts. The flaw highlights a common pitfall in backend development where global role permissions are assumed to override local resource-specific constraints without explicit validation of the target resource's identity during the authorization phase.
Mitigation strategies must focus on correcting the authorization logic to ensure channel context is preserved throughout the permission evaluation process. Developers should modify the checkPermission call within setChannel to explicitly include the request's channel_id in the options object, ensuring that p_channel_id is not null when passed to rbac_check_permission_direct. This will force the system to evaluate per-channel allow and deny overrides as intended by the security model. Additionally, implementing a defense-in-depth approach where resource-level validation occurs before or concurrently with authorization checks can prevent such bypasses. Until a patched version is released, administrators should restrict API key permissions to the minimum necessary scope and monitor for unusual bundle promotion activities across channels that have explicit denial policies in place.