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

> Authenticated attackers can view other users' form submissions by guessing or modifying submission reference codes.

- **Severity:** Medium 6.5 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 11 Mar 2026
- **Updated:** 11 Mar 2026
- **Also known as:** GHSA-2g49-rfm6-5qj5

## What is CVE-2026-28803?

CVE-2026-28803 is a medium-severity missing authorization vulnerability in open-formulieren open-forms, published on 11 Mar 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official 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.

Weakness: CWE-284 (Improper Access Control)

## Which versions are affected by CVE-2026-28803?

It affects 1 product.


Products: Maykinmedia Open Forms.

## How do I fix CVE-2026-28803?

No fix has been published for CVE-2026-28803 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-28803 being exploited?

There is no known exploitation of CVE-2026-28803 in the wild and no public exploit code.

## Other vulnerabilities in open-formulieren open-forms

- [CVE-2024-24771](https://insights.sbomify.com/CVE-2024-24771/): Open Forms potential multi-factor authentication bypass (high 7.7)
- [CVE-2022-31041](https://insights.sbomify.com/CVE-2022-31041/): Insufficient content-type validation for uploaded files in open-forms (high 7.6)
- [CVE-2022-31040](https://insights.sbomify.com/CVE-2022-31040/): Open Redirect in open-forms (high 7.1)
- [CVE-2025-64515](https://insights.sbomify.com/CVE-2025-64515/): Open Forms prefill data in read-only components can be tampered (medium 4.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-28803 and fix it if it is affected.

What it is: CVE-2026-28803 is a medium-severity missing authorization vulnerability in open-formulieren open-forms, published on 11 Mar 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-28803 in the wild and no public exploit code.

Affected product: open-formulieren open-forms. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-28803/ (Markdown: https://insights.sbomify.com/CVE-2026-28803/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-28803
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-28803
- OSV: https://osv.dev/vulnerability/CVE-2026-28803

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-28803/
Summaries are generated and may contain mistakes; the official description above is the record.