What is CVE-2026-28803?

CVE-2026-28803 is a medium-severity vulnerability in Maykinmedia Open Forms, classified under Improper Access Control. CVSS score: 6.5/10. Published 2026-03-11.

How severe is CVE-2026-28803?

Medium severity. CVSS v3 base score is 6.5 out of 10.

Vulnerability in Maykinmedia Open Forms

CVE-2026-28803

Open Forms allows users create and publish smart forms. Prior to 3.3.13 and 3.4.5, to be able to cosign, the cosigner receives an e-mail with instructions or a deep-link to start the cosign flow. The submission reference is communicated so that the user can retrieve the submission to be cosigned. Attackers can guess a code or modify the received code to look up arbitrary submissions, after logging in (with DigiD/eHerkenning/... depending on form configuration). This vulnerability is fixed in 3.3.13 and 3.4.5.

EPSS: 0.002 (10.2th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N.

Affected products

Maykinmedia Open_forms
Open-formulieren Open-forms — versions >= 3.4.0-alpha.0, < 3.4.5, < 3.3.13

Weakness classification (CWE)

CWE-284 — Improper Access Control

References

security-advisories@github.com (x_refsource_CONFIRM, Mitigation, Vendor Advisory)

Frequently asked questions

What is CVE-2026-28803?: CVE-2026-28803 is a medium-severity vulnerability in Maykinmedia Open Forms, classified under Improper Access Control. CVSS score: 6.5/10. Published 2026-03-11.
How severe is CVE-2026-28803?: Medium severity. CVSS v3 base score is 6.5 out of 10.