Vikunja has a 2FA Bypass via Caldav Basic Auth

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

6.9 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N · score source

EPSS

• CVE-2026-33315: 0.31% estimated exploitation activity in the next 30 days; percentile 24.38 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary The Caldav endpoint allows login using Basic Authentication, which in turn allows users to bypass the TOTP on 2FA-enabled accounts. The user can then access standard project information that would normally be protected behind 2FA (if enabled), such as project name, description, etc. Details The two files below show that when a user is accessing Caldav via Basic Authentication, it skips all steps involving 2FA. The order of operations is essentially: 1. Retrieve basic credentials. 2. Verify username. 3. Verify password. 4. Success pkg/routes/caldav/auth.go:45 pkg/user/user.go:358 PoC 1. Setup a Docker instance of Vikunja v2.1.0 and create an account. Enable 2FA on the account. <img width="1506" height="646" alt="CleanShot 2026-03-16 at 15 30 24@2x" src="https://github.com/user-attachments/assets/e88522af-4333-4758-8ba4-3e34de9680f7" / 2. Logout of the account. 3. Using a web proxy, such as Burp Suite, craft an HTTP request to the endpoint similar to the one shown below. Ensure…

Published by the source

20 Mar 2026, 17:25 UTC

Last modified by the source

25 Mar 2026, 20:53 UTC

Source last checked

26 Oct 2026, 15:18 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-47cr-f226-r4pq

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2026-33315

Advisory: Vikunja has a 2FA Bypass via Caldav Basic Auth
IDs: CVE-2026-33315, GHSA-47cr-f226-r4pq
Record: https://patchnext.com/advisories/cve-2026-33315 (revision 1, source checked 26 Oct 2026, 15:18 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.9)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor response not established. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go code.vikunja.io/api: affected <= 2.1.0

## Suggested inspection (read-only)
- Go code.vikunja.io/api: check the installed version with your package manager.

## Supported action
No complete vendor fix is recorded. Follow the primary source's mitigation guidance and check this record again before closing anything.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on code.vikunja.io/api.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-47cr-f226-r4pq (GitHub-reviewed advisory GHSA-47cr-f226-r4pq lists affected ranges: Go code.vikunja.io/api >=0 <=2.1.0)

Commands are suggestions: review each one before running it.