What is the CVSS score of CVE-2026-28803?

CVE-2026-28803 has a CVSS 3.1 base score of 6.5 (Medium). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N. EPSS exploitation probability: 0.0%.

Which versions of Open Forms are affected by CVE-2026-28803?

Organizations using Open Forms should be aware of notable risk from CVE-2026-28803, a improper access control vulnerability rated CVSS 6.5.

How to fix or mitigate CVE-2026-28803?

Within 30 days: Identify affected systems and apply vendor patches as part of regular patch cycle. Monitor vendor channels for patch availability.

Open Forms CVE-2026-28803

MEDIUM

Improper Access Control (CWE-284)

2026-03-11 security-advisories@github.com

Authentication Bypass Open Forms

6.5

CVSS 3.1 · GitHub Advisory

Severity by source

GitHub Advisory PRIMARY

6.5 MEDIUM

AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

Primary rating from GitHub Advisory · only source for this CVE.

CVSS VectorGitHub Advisory

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

Attack Vector

Network

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

None

Availability

None

Lifecycle Timeline

Analysis Generated

Mar 12, 2026 - 22:06 vuln.today

CVE Published

Mar 11, 2026 - 16:16 nvd

MEDIUM 6.5

DescriptionGitHub Advisory

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.

AnalysisAI

Open Forms versions prior to 3.3.13 and 3.4.5 allow authenticated attackers to access arbitrary form submissions through submission reference enumeration or manipulation in the cosigning workflow. An attacker with valid credentials can guess or modify cosigner codes to retrieve submissions they should not have access to, resulting in unauthorized information disclosure.

Technical ContextAI

This vulnerability (CWE-284: Improper Access Control) affects Open Forms allows users create and publish smart forms.. 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