Vikunja: WebSocket authentication ignores server-side session state, so revoked sessions keep receiving live pushes

Summary

Vikunja v2.6.0 introduced server-side sessions with revocation semantics: DELETE /api/v2/user/sessions/{id} documents "Revokes a specific session by its UUID", and enabling TOTP calls DeleteAllUserSessions to invalidate all sessions. The WebSocket endpoint accepts any cryptographically valid user JWT without ever resolving its sid (session id) claim against the sessions table. A connection authenticated before revocation stays authenticated and continues to receive live pushes indefinitely, and even brand-new WebSocket connections are accepted with a token whose session was deleted. The revocation feature therefore does not cover the WebSocket boundary at all.

Details

User access JWTs carry a session reference: NewUserJWTAuthtoken (pkg/modules/auth/auth.go:188) sets claims["sid"] = sessionID, and the API login-session documentation describes the claim as tying the JWT to a server-side session. On the HTTP side nothing consumes the claim per request either (REST access tokens simply expire after their short TTL, a design the maintainers documented when fixing GHSA-96q5, and refresh tokens are correctly invalidated when the session row is deleted).

The WebSocket endpoint GET /api/v2/ws authenticates through the first client message. Connection.handleAuth (pkg/websocket/connection.go:168) validates the token exclusively with auth.GetUserIDFromToken (pkg/modules/auth/auth.go:292):

func GetUserIDFromToken(tokenString string) (int64, error) {
	token, err := jwt.Parse(tokenString, func(_ *jwt.Token) (any, error) {
		return []byte(config.ServiceSecret.GetString()), nil
	})
	...
	typ, ok := claims["type"].(float64)
	if !ok || int(typ) != AuthTypeUser {
		return 0, jwt.ErrTokenInvalidClaims
	}
	...
}

The function verifies signature and token type only. No session lookup occurs anywhere in the WebSocket path, and no re-validation happens after the initial auth. Consequently:

1. A connection authenticated before DELETE /api/v2/user/sessions/{id} (or before TOTP enable, which runs models.DeleteAllUserSessions, pkg/routes/api/v2/user_totp.go:208) remains registered in the hub and keeps receiving every subscribed event, such as notification.created with the full notification object including comment, task and project content.
2. A new connection opened after the deletion, using the same pre-revocation token, authenticates successfully.
3. Session deletion is observable only in the REST surface. The user's session list empties, the refresh token dies on next use, but the WebSocket channel never notices.