Maven · nl.nl-portal:taak
NL Portal: IDOR allows any authenticated user to complete and tamper with another user's taak
In versions from 1.5.0 up to and including 3.0.0, any authenticated portal user could complete and tamper with another user's open task by submitting it on their behalf. The task submission endpoint accepted a task ID and a payload, but it never checked whether the task actually belonged to the user making the call.
An attacker who held a valid login (a normal burger OAuth token) and who knew or guessed another user's task ID could:
verzonden_data — with arbitrary input of their choosing.Functionally this means a malicious authenticated user could submit and alter forms in any other user's name, while at the same time reading what that user had previously filled in. Both the integrity of submitted data and the confidentiality of form contents are affected.
The vulnerable code was introduced together with the Taak V2 implementation (commit bb1c1ecf, 2024-06-04) and first shipped in the 1.5.x release line. Earlier 1.x releases did not contain this resolver.
Upgrade to 3.0.1 or later.
Fix commit: 8e699add — "Add auth check for task submission".
Until the upgrade is applied, block the submitTaakV2 GraphQL mutation at the API gateway, or restrict the /graphql endpoint to trusted networks.
The resolver nl.nlportal.zgw.taak.service.TaakService.submitTaakV2(id, submission, authentication) fetched the task object by UUID and immediately transitioned it to the AFGEROND state, writing record.data.portaalformulier.verzondenData from caller-supplied input. No check verified that the task's identificatie matched the authenticated burger.
The fix adds a call to a new isAuthorizedForTaak(authentication, objectsApiTask) before the status change. The check compares identificatie.type and identificatie.value against the authenticated principal and validates the task's eigenaar for bedrijf machtigingen.
Discovered during the nl-portal-backend-libraries penetration testing engagement (phase 1, May 2026). Vendor attribution to be added before publication.
Is your project exposed to this? Stateward checks every dependency on every pull request and flags it only if your code actually reaches it.
Check my repoSources: CISA KEV (public domain), OSV.dev & GitHub Advisory Database (CC-BY-4.0), FIRST EPSS, NVD/CWE (public domain). Served live from the Stateward advisory database.