{"schema":"threatline.record/2","record":{"id":"GHSA-w2ch-4xgr-22ww","aliases":["GHSA-w2ch-4xgr-22ww","GO-2026-6754"],"summary":"Vikunja: Task relation deletion does not check read access to the other task, allowing cross-project relation removal","details":"## Summary\n\nDeleting a task relation only requires write access on the base task. Unlike relation creation, it does not verify that the caller can read the other task. A user with write access to one project can therefore delete relations whose other end lives in a project they have no access to. Since the delete removes both the forward and inverse rows, the relation also disappears for the other project's members.\n\n## Details\n\n`TaskRelation.CanCreate` (`pkg/models/task_relation_permissions.go:32-52`) requires write access on `TaskID` **and** read access on `OtherTaskID`.\n\n`TaskRelation.CanDelete` (`pkg/models/task_relation_permissions.go:25-29`) only checks `Task{ID: rel.TaskID}.CanUpdate(s, a)`; `OtherTaskID` is never authorized.\n\n`TaskRelation.Delete` (`pkg/models/task_relation.go:314-354`) then deletes both the `(task_id, other_task_id, kind)` row and its inverse, so the relation is removed from the far task as well.\n\nAffects `DELETE /api/v1/tasks/{id}/relations/{kind}/{otherTaskId}` and the equivalent v2 endpoint.\n\n## Impact\n\nLow, integrity only. An authenticated user holding write permission on a shared project can remove task relations that link into projects they cannot read. No data is disclosed and no privilege is gained; the attacker cannot recreate the relation. The far project's owner sees the relation vanish without indication of who removed it.\n\nPreconditions: the attacker has write access to a project containing a task that is already related to a task in a project they cannot access.\n\n## Proof of Concept\n\n1. As `owner`, create project `P_near` with task `near` and project `P_far` with task `far`.\n2. Share `P_near` with `attacker` at write permission (`permission: 1`). Do not share `P_far`.\n3. As `owner`: `PUT /api/v1/tasks/{near}/relations` with `{\"other_task_id\": far, \"relation_kind\": \"related\"}` -> 200.\n4. As `attacker`: `GET /api/v1/tasks/{far}` -> 403 (confirms no access).\n5. As `attacker`: `PUT /api/v1/tasks/{near}/relations` with the same body -> 403 (create path is enforced).\n6. As `attacker`: `DELETE /api/v1/tasks/{near}/relations/related/{far}` -> 200 `\"Successfully deleted.\"`\n7. As `owner`: `GET /api/v1/tasks/{far}` -> `related_tasks` is now empty.\n\nReproduced against `vikunja/vikunja:2.5.0`.\n\n## Recommended Fix\n\nMake `CanDelete` mirror `CanCreate`: after checking `CanUpdate` on the base task, also require `CanRead` on `OtherTaskID`.","categories":["Libraries & packages"],"product":"code.vikunja.io/api","vendor":"","ecosystem":"go","affected_ranges":[{"source":"GitHub Advisory Database","source_url":"https://github.com/advisories/GHSA-w2ch-4xgr-22ww","source_modified_at":"2026-10-09T20:54:52Z","fetched_at":"2026-10-23T18:42:43.628194Z","package":{"ecosystem":"go","name":"code.vikunja.io/api"},"range":">= 0.9, <= 2.5.0"},{"source":"OSV","source_url":"https://osv.dev/vulnerability/GHSA-w2ch-4xgr-22ww","source_modified_at":"2026-10-19T21:41:23.229510718Z","fetched_at":"2026-10-23T18:45:31.882637Z","package":{"name":"code.vikunja.io/api","ecosystem":"Go","purl":"pkg:golang/code.vikunja.io/api"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0.9"},{"fixed":"2.6.0"}]}],"versions":[]}],"fixed_versions":[{"source":"GitHub Advisory Database","source_url":"https://github.com/advisories/GHSA-w2ch-4xgr-22ww","source_modified_at":"2026-10-09T20:54:52Z","fetched_at":"2026-10-23T18:42:43.628194Z","package":{"ecosystem":"go","name":"code.vikunja.io/api"},"version":"2.6.0"},{"source":"OSV","source_url":"https://osv.dev/vulnerability/GHSA-w2ch-4xgr-22ww","source_modified_at":"2026-10-19T21:41:23.229510718Z","fetched_at":"2026-10-23T18:45:31.882637Z","package":{"name":"code.vikunja.io/api","ecosystem":"Go","purl":"pkg:golang/code.vikunja.io/api"},"version":"2.6.0"}],"cvss":2.3,"severity":"Low","kev":{"listed":false},"epss":{"probability":null,"percentile":null,"score_date":null},"published_at":"2026-10-09T20:54:52Z","modified_at":"2026-10-19T21:41:23.229510718Z","provenance":[{"source":"GitHub Advisory Database","url":"https://github.com/advisories/GHSA-w2ch-4xgr-22ww","fetched_at":"2026-10-23T18:42:43.628194Z","source_modified_at":"2026-10-09T20:54:52Z"},{"source":"OSV","url":"https://osv.dev/vulnerability/GHSA-w2ch-4xgr-22ww","fetched_at":"2026-10-23T18:45:31.882637Z","source_modified_at":"2026-10-19T21:41:23.229510718Z"}],"sources":["GitHub Advisory Database","OSV"],"references":[{"url":"https://github.com/go-vikunja/vikunja/security/advisories/GHSA-w2ch-4xgr-22ww","source":"GitHub Advisory Database"},{"url":"https://github.com/go-vikunja/vikunja/pull/3688","source":"GitHub Advisory Database"},{"url":"https://github.com/go-vikunja/vikunja/commit/077dc4de79ce6f1ab59215a2c7bf9b30423685f2","source":"GitHub Advisory Database"},{"url":"https://github.com/go-vikunja/vikunja/releases/tag/v2.6.0","source":"GitHub Advisory Database"},{"url":"https://github.com/advisories/GHSA-w2ch-4xgr-22ww","source":"GitHub Advisory Database"}],"locations":[],"motoko_assessment":{"status":"requires_architecture_review","automatic_remediation":false},"classification":{"method":"product-first software-layer rules","rules_version":"2.1","matched_on":"ecosystem","confidence":"heuristic","reviewed":false},"change_timestamp":"2026-10-19T21:41:23.229510718Z","content_hash":"c23fb07d3080f466d794b0f4bb55ab603fe3ac9b27b036318a9811641908baee"}}