vulnerability / NVI-00012058 / Revision 1
Vikunja: CalDAV relation creation bypasses TaskRelation.CanCreate, allowing an unauthorized write into any task by known UID
GitHub lists this reviewed advisory for code.vikunja.io/api. Published version ranges and source prerequisites are shown below; this is not an inspection of a visitor’s application.
This report has not inspected your inventory, configuration, deployed build, reachability or evidence. A catalog listing and a severity score do not establish exposure or compromise.
01 / Meaning
Why it matters
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02 / Applicability
The affected context
Affected versions, configuration prerequisites and known exclusions are public. Confirm each one against the deployed service.
code.vikunja.io/api
source listed<= 2.5.0
### Summary Creating a task relation over CalDAV does not run the `TaskRelation.CanCreate` permission check that the REST API enforces. An attacker can attach a relation to any task whose UID they know, including tasks in projects they have no access to. The identical operation over REST is correctly refused with 403. ### Details `persistRelations` (`pkg/routes/caldav/listStorageProvider.go`, ~line 986) resolves the related task with an **unscoped** UID lookup (`models.GetTaskSimpleByUUID`) and calls `rel.Create(s, a)` directly, with no `CanCreate` check. `pkg/caldav/parsing.go` maps `RELATED-TO;RELTYPE=CHILD` to `RelationKindSubtask`. Because the CalDAV path never invokes the model's permission method, an authenticated user can create a subtask/parent relation between a task they own and an arbitrary victim task identified only by its UID. Task UIDs are `json:"-"` (never exposed over REST) but are exposed over CalDAV to anyone who has ever had read access to the containing project. Revoking that access does not unlearn the UID, so the realistic attacker is a removed collaborator. This write primitive also feeds the cross-project subtask-disclosure issue (GHSA-3hc7-r24j-rpwc): i
03 / Response
What to do next
- investigate
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04 / Limits
What this report cannot establish
- Customer inventory, deployment, reachability and exploitation have not been inspected.
05 / Provenance
Sources you can inspect
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- GHSA-g38j-7v97-x298 ↗
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Public revision history
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- Revision 1 ·
First indexed by Null; source disclosure date is shown separately.