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HIGH severity

CVE-2026-49464 — taak

HIGH

CVE-2026-49464 is a high-severity (CVSS 8.1) CWE-639 vulnerability in nl.nl-portal:taak. A fix is available for nl.nl-portal:taak — see the affected versions and patch details below.

NL Portal: IDOR allows any authenticated user to complete and tamper with another user's taak

Also known asGHSA-6h3c-r723-7fx3
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Oct 6, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

  • A successful exploit gives an attacker total control of the affected component, not partial access.
  • CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-49464.

EPSS Exploitation Probability

via FIRST.org ↗
0.4%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs26th percentile — riskier than 26% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2026-49464 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 383,485 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

1 pkg affected
☕nl.nl-portal:taak

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.

Description

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.

Patches

Upgrade to 3.0.1 or later.

Fix commit: 8e699add — "Add auth check for task submission".

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.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
☕Mavennl.nl-portal:taak≥ 1.5.0&&< 3.0.13.0.1nl.nl-portal:taak:3.0.1

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for nl.nl-portal:taak, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update nl.nl-portal:taak to 3.0.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-49464 is resolved across your whole dependency graph.

  3. Workarounds

    If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

## 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 choosi
O3 Security · Impact-Aware SCA

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CVE-2026-49464: taak — Fixed in 3.0.1 | O3 Security