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

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

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.

Products include Vikunja Vikunja.

How do I fix CVE-2026-40103?

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

Upgrade, and check permissions on every request on the server, not only in the interface. More about Missing authorization.

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 Vikunja Vulnerable to Account Takeover via Password Reset Token Reuse Critical 9.8
• CVE-2026-27575 Vijkunja has Weak Password Policy Combined with Persistent Sessions After Password Change Critical 9.1
• CVE-2026-25935 Vikunja Affected by XSS Via Task Preview High 8.6
• CVE-2026-35595 Vikunja Affected by Privilege Escalation via Project Reparenting High 8.3
• CVE-2026-33316 Vikunja’s Improper Access Control Enables Bypass of Administrator-Imposed Account Disablement High 8.1

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as GHSA-v479-vf79-mg83, GO-2026-5650.