---
id: CVE-2026-88862
title: >-
  Capgo (capgo.app) backend through 12.242.4 does not validate parent-child
  delegation when processing the x-limited-key-id header
summary: >-
  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 num…
severity: high
cvss: 8.8
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H'
cwe:
  - CWE-863
vendor: Cap-go
product: capgo.app
affected:
  - capgo.app
published: '2026-09-10'
updated: '2026-09-10'
sourceUpdated: '2026-09-10T15:17:56.617'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-88862'
references:
  - url: >-
      https://github.com/Cap-go/capgo.app/security/advisories/GHSA-5hjr-xhx8-x5j7
    label: disclosure@vulncheck.com
  - url: >-
      https://www.vulncheck.com/advisories/capgo-api-key-manager-authentication-bypass-via-x-limited-key-id
    label: disclosure@vulncheck.com
  - url: >-
      https://github.com/Cap-go/capgo.app/security/advisories/GHSA-5hjr-xhx8-x5j7
    label: 134c704f-9b21-4f2e-91b3-4a467353bcc0
tags:
  - nvd
  - cve.org
  - exploit-available
exploitAvailable: true
ssvc:
  exploitation: poc
  automatable: 'no'
  technicalImpact: total
  timestamp: '2026-09-10T14:26:27.714255Z'
ingestedAt: '2026-09-10T13:50:37.334Z'
epss: 0.00442
epssPercentile: 0.35802
---

## Overview

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.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.