# CVE-2026-40103: Vikunja's Scoped API tokens with projects.background permission can delete project backgrounds

> Attackers with scoped API tokens can delete project backgrounds due to method confusion in authorization checks.

- **Severity:** Medium 4.3 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/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:** Yes
- **Published:** 10 Apr 2026
- **Updated:** 15 Apr 2026
- **Also known as:** GHSA-v479-vf79-mg83, GO-2026-5650

## What is CVE-2026-40103?

CVE-2026-40103 is a medium-severity missing authorization vulnerability in go-vikunja vikunja, published on 10 Apr 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

Vikunja is an open-source self-hosted task management platform. Prior to 2.3.0, Vikunja's scoped API token enforcement for custom project background routes is method-confused. A token with only projects.background can successfully delete a project background, while a token with only projects.background_delete is rejected. This is a scoped-token authorization bypass. This vulnerability is fixed in 2.3.0.

Weakness: CWE-836 (Use of Password Hash Instead of Password for Authentication)

## Which versions are affected by CVE-2026-40103?

3 open source packages ship an affected version, including code.vikunja.io/api. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `code.vikunja.io/api` | Go | All versions | None |
| `code.vikunja.io/api` | Go | All versions | 2.3.0 |
| `code.vikunja.io/api` | Go | All versions | 2.3.0 |

Products: Vikunja Vikunja.

## How do I fix CVE-2026-40103?

Upgrade code.vikunja.io/api to 2.3.0 or later.

## Is CVE-2026-40103 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-40103 exists.

## Other vulnerabilities in go-vikunja vikunja

- [CVE-2026-28268](https://insights.sbomify.com/CVE-2026-28268/): Vikunja Vulnerable to Account Takeover via Password Reset Token Reuse (critical 9.8)
- [CVE-2026-27575](https://insights.sbomify.com/CVE-2026-27575/): Vijkunja has Weak Password Policy Combined with Persistent Sessions After Password Change (critical 9.1)
- [CVE-2026-25935](https://insights.sbomify.com/CVE-2026-25935/): Vikunja Affected by XSS Via Task Preview (high 8.6)
- [CVE-2026-35595](https://insights.sbomify.com/CVE-2026-35595/): Vikunja Affected by Privilege Escalation via Project Reparenting (high 8.3)
- [CVE-2026-33316](https://insights.sbomify.com/CVE-2026-33316/): Vikunja’s Improper Access Control Enables Bypass of Administrator-Imposed Account Disablement (high 8.1)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-40103 and fix it if it is affected.

What it is: CVE-2026-40103 is a medium-severity missing authorization vulnerability in go-vikunja vikunja, published on 10 Apr 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-40103 exists.

Affected packages and fixed versions:
- code.vikunja.io/api (Go): affected all versions; no fix listed
- code.vikunja.io/api (Go): affected all versions; fixed in 2.3.0
- code.vikunja.io/api (Go): affected all versions; fixed in 2.3.0

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-2026-40103/ (Markdown: https://insights.sbomify.com/CVE-2026-40103/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-40103
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-40103
- OSV: https://osv.dev/vulnerability/CVE-2026-40103

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-40103/
Summaries are generated and may contain mistakes; the official description above is the record.