How severe is CVE-2026-28803?

CVE-2026-28803 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability none.

Is CVE-2026-28803 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (10th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-28803?

CVE-2026-28803 affects Maykinmedia Open Forms. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-28803?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2026-28803 have an EU (EUVD) identifier?

Yes. CVE-2026-28803 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-11198.

When was CVE-2026-28803 published?

CVE-2026-28803 was published on 2026-03-11 and last updated on 2026-06-17.

CVE-2026-28803

CVE-2026-28803 is a medium-severity vulnerability in Maykinmedia Open Forms with a CVSS 3.x base score of 6.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-284.

Key facts

Severity: Medium (CVSS 3.x base score 6.5)
EPSS exploit prediction: 0% (10th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-11198
Weakness: CWE-284
Affected product: Maykinmedia Open Forms
Published: 2026-03-11
Last modified: 2026-06-17

Description

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.

Frequently asked questions

What is 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.
How severe is CVE-2026-28803?: CVE-2026-28803 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability none.
Is CVE-2026-28803 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (10th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-28803?: CVE-2026-28803 affects Maykinmedia Open Forms. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-28803?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-28803 have an EU (EUVD) identifier?: Yes. CVE-2026-28803 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-11198.
When was CVE-2026-28803 published?: CVE-2026-28803 was published on 2026-03-11 and last updated on 2026-06-17.

References

https://github.com/open-formulieren/open-forms/security/advisories/GHSA-2g49-rfm6-5qj5

Affected products (1)

cpe:2.3:a:maykinmedia:open_forms:*:*:*:*:*:*:*:*

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