{"id":"GHSA-v479-vf79-mg83","summary":"Vikunja: Scoped API tokens with projects.background permission can delete project backgrounds","details":"### Summary\n\nVikunja's scoped API token enforcement for custom project background routes is method-confused. A token with only `projects.background` can successfully delete a project background, while a token with only `projects.background_delete` is rejected.\n\nThis is a scoped-token authorization bypass.\n\n### Details\n\nI verified this locally on commit `c5450fb55f5192508638cbb3a6956438452a712e`.\n\nRelevant code paths:\n* `pkg/models/api_routes.go`\n* `pkg/routes/routes.go`\n* `pkg/modules/background/handler/background.go`\n\nRoute registration exposes separate permissions for the same path:\n* `GET /api/v1/projects/:project/background` -\u003e `projects.background`\n* `DELETE /api/v1/projects/:project/background` -\u003e `projects.background_delete`\n\nAt enforcement time, `CanDoAPIRoute()` falls back to the parent group and reconstructs the child permission from the path segments only. For the DELETE request, that becomes `background`, so the matcher accepts any token containing `projects.background` without re-checking the HTTP method or matching the stored route detail.\n\nThis matters because `RemoveProjectBackground()` is a real destructive operation:\n* It checks project update rights.\n* It deletes the background file if present.\n* It clears the project's `BackgroundFileID`.\n\n### PoC\n\n1. Log in as a user who can update a project that already has a background.\n2. Create an API token with only:\n   `{\"projects\":[\"background\"]}`\n3. Send:\n   `DELETE /api/v1/projects/\u003cproject_id\u003e/background`\n   `Authorization: Bearer \u003ctoken\u003e`\n4. Observe that the request succeeds and the project background is removed.\n\n**For comparison:**\n1. Create an API token with only:\n   `{\"projects\":[\"background_delete\"]}`\n2. Repeat the same DELETE request.\n3. Observe that the request is rejected with `401 Unauthorized`.\n\nI confirmed this locally with three validations:\n1. `/api/v1/routes` advertises both `background` and `background_delete`.\n2. The matcher unit test proves `CanDoAPIRoute()` accepts DELETE for `background`.\n3. The webtest proves a real API token with only `background` successfully deletes the background.\n\n### Impact\n\nScoped API tokens can exceed their intended capability. A token intended for project background access can delete project backgrounds, which weakens the trust model for automation and third-party integrations that rely on narrowly scoped tokens.\n\nThe attacker needs a valid API token created by a user who has update rights on the target project, but the token itself only needs the weaker `projects.background` permission.","aliases":["CVE-2026-40103","GO-2026-5650"],"modified":"2026-06-25T23:11:19.763837988Z","published":"2026-04-10T15:36:47Z","database_specific":{"cwe_ids":["CWE-836","CWE-863"],"severity":"MODERATE","github_reviewed":true,"github_reviewed_at":"2026-04-10T15:36:47Z","nvd_published_at":"2026-04-10T17:17:13Z"},"references":[{"type":"WEB","url":"https://github.com/go-vikunja/vikunja/security/advisories/GHSA-v479-vf79-mg83"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-40103"},{"type":"WEB","url":"https://github.com/go-vikunja/vikunja/pull/2584"},{"type":"WEB","url":"https://github.com/go-vikunja/vikunja/commit/6a0f39b252a81fa4b19dc56dc889183acc9225ae"},{"type":"PACKAGE","url":"https://github.com/go-vikunja/vikunja"},{"type":"WEB","url":"https://github.com/go-vikunja/vikunja/releases/tag/v2.3.0"}],"affected":[{"package":{"name":"code.vikunja.io/api","ecosystem":"Go","purl":"pkg:golang/code.vikunja.io/api"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"2.3.0"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/04/GHSA-v479-vf79-mg83/GHSA-v479-vf79-mg83.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L"}]}