CVE-2026-28803: Open Forms possible to view submission details of other people than intended

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.

CVSS vector

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

Attack vector

Network

Complexity

Low

Privileges

Low

User interaction

None

Confidentiality

High

Integrity

None

Availability

None

Scope

Unchanged

Exploitation

Is it being used?

Exploit prediction (EPSS)0.2% · higher than 12% of CVEs

Exploited in the wildNo evidence yet

CISA KEVNot listed

Ransomware campaign useNot known

Affected products

Which versions

OP

open-forms · open-formulieren

>= 3.4.0-alpha.0, < 3.4.5; < 3.3.13 · source: vendor

OF

Open Forms · Maykinmedia

before 3.3.13; 3.4.0 before 3.4.5 · source: NVD