Cap-go Capgo up to 12.242.4 RBAC Middleware hono_middleware.ts privileges management

Summaryinfo

A vulnerability was found in Cap-go Capgo up to 12.242.4. It has been classified as critical. This issue affects the function checkKeyByIdPg/hasLimitedRbacSubkeyScope/validateSubkeyUser of the file supabase/functions/_backend/utils/hono_middleware.ts of the component RBAC Middleware. This manipulation causes privileges management. This vulnerability appears as CVE-2026-88862. The attack may be initiated remotely. There is no available exploit.

Detailsinfo

A vulnerability has been found in Cap-go Capgo up to 12.242.4 and classified as critical. Affected by this vulnerability is the function checkKeyByIdPg/hasLimitedRbacSubkeyScope/validateSubkeyUser of the file supabase/functions/_backend/utils/hono_middleware.ts of the component RBAC Middleware. The manipulation with an unknown input leads to a privileges management vulnerability. The CWE definition for the vulnerability is CWE-269. The product does not properly assign, modify, track, or check privileges for an actor, creating an unintended sphere of control for that actor. As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

Capgo (capgo.app) backend through 12.242.4 does not validate parent-child delegation when processing the x-limited-key-id header. checkKeyByIdPg() in supabase/functions/_backend/utils/hono_middleware.ts resolves the attacker-supplied numeric API key ID using only the key ID, its expiration state, and the authenticating key's user_id, while hasLimitedRbacSubkeyScope() accepts any key with a non-organization (e.g., app-scoped) RBAC binding and validateSubkeyUser() only compares owning user IDs. Because Capgo treats API keys as independent RBAC principals with separate role bindings, an authenticated apikey_manager API key with no application access can supply the numeric ID of a more privileged same-owner key and have the middleware replace the authenticated principal and effective API-key secret with that key (setSubkeyAuthContext), exercising an app_admin sibling's permissions without knowing or submitting its secret. The issue was reproduced on release 12.242.4 (commit b3d02cdbc23ac59990785acacd1f113c07458568) after the fix for GHSA-8h52-44r7-w343; at the time of the advisory no patched version was available.

It is possible to read the advisory at github.com. This vulnerability is known as CVE-2026-88862 since 09/10/2026. The exploitation appears to be easy. The attack can be launched remotely. Technical details of the vulnerability are known, but there is no available exploit. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 09/10/2026). The attack technique deployed by this issue is T1068 according to MITRE ATT&CK.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

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Productinfo

Vendor

• Cap-go

Name

• Capgo

Version

• 12.242.0
• 12.242.1
• 12.242.2
• 12.242.3
• 12.242.4

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CPE 2.2info

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