EUVD-2026-290879

fkie_cve-2026-34727

Vikunja is an open-source self-hosted task management platform. Prior to 2.3.0, the OIDC callback handler issues a full JWT token without checking whether the matched user has TOTP two-factor authentication enabled. When a local user with TOTP enrolled is matched via the OIDC email fallback mechanism, the second factor is completely skipped. This vulnerability is fixed in 2.3.0.

GHSA-8jvc-mcx6-r4cg — Vikunja has TOTP Two-Factor Authentication Bypass via OIDC Login Path

Affected: Go: code.vikunja.io/api

## Summary

The OIDC callback handler issues a full JWT token without checking whether the matched user has TOTP two-factor authentication enabled. When a local user with TOTP enrolled is matched via the OIDC email fallback mechanism, the second factor is completely skipped.

## Details

The OIDC callback at `pkg/modules/auth/openid/openid.go:185` issues a JWT directly after user lookup:

```go return auth.NewUserAuthTokenResponse(u, c, false) ```

There are zero references to TOTP in the entire `pkg/modules/auth/openid/` directory. By contrast, the local login handler at `pkg/routes/api/v1/login.go:79-102` correctly implements TOTP verification:

```go totpEnabled, err := user2.TOTPEnabledForUser(s, user) if totpEnabled { if u.TOTPPasscode == "" { _ = s.Rollback() return user2.ErrInvalidTOTPPasscode{} } _, err = user2.ValidateTOTPPasscode(s, &user2.TOTPPasscode{ User: user, Passcode: u.TOTPPasscode, }) ```

When OIDC `EmailFallback` maps to a local user who has TOTP enabled, the TOTP enrollment is ignored and a full JWT is issued without any second-factor challenge.

## Proof of Concept

Tested on Vikunja v2.2.2 with Dex as the OIDC provider.

Setup: - Vikunja configured with `emailfallback: true` for Dex - Local user `alice` (id=1) has TOTP enabled

```python import requests, re, html from urllib.parse import parse_qs, urlparse

TARGET = "http://localhost:3456" DEX = "http://localhost:5556" API = f"{TARGET}/api/v1"

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EUVD-2026-290879

fkie_cve-2026-34727

GHSA-8jvc-mcx6-r4cg — Vikunja has TOTP Two-Factor Authentication Bypass via OIDC Login Path