Summary
NL Portal: IDOR allows any authenticated user to complete and tamper with another user's taak
Full technical description
Workarounds
Until the upgrade is applied, block the submitTaakV2 GraphQL mutation at the API gateway, or restrict the /graphql endpoint to trusted networks.
Technical details
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.
Credits
Discovered during the nl-portal-backend-libraries penetration testing engagement (phase 1, May 2026). Vendor attribution to be added before publication.
Impact
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:
- Mark someone else's task as completed.
- Overwrite the data submitted with that task, the
verzonden_data, with arbitrary input of their choosing. - Receive the full task back in the GraphQL response, including the form data that the legitimate owner had already entered. This leaks personal data belonging to the original user.
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.
CVE-2026-49464 has a CVSS score of 8.1 (High). The vector is network-reachable, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (3.0.1); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Upgrade to 3.0.1 or later.
Fix commit: 8e699add, "Add auth check for task submission".
Frequently Asked Questions
- What is CVE-2026-49464? CVE-2026-49464 is a high-severity security vulnerability in nl.nl-portal:taak (maven), affecting versions >= 1.5.0, <= 3.0.0. It is fixed in 3.0.1.
- How severe is CVE-2026-49464? CVE-2026-49464 has a CVSS score of 8.1 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of nl.nl-portal:taak are affected by CVE-2026-49464? nl.nl-portal:taak (maven) versions >= 1.5.0, <= 3.0.0 is affected.
- Is there a fix for CVE-2026-49464? Yes. CVE-2026-49464 is fixed in 3.0.1. Upgrade to this version or later.
- Is CVE-2026-49464 exploitable, and should I be worried? Whether CVE-2026-49464 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-49464 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-49464? Upgrade
nl.nl-portal:taakto 3.0.1 or later.