fix(cve): run switch commands as normal user on Windows to prevent privilege escalation

CVE-2026-41477

src/apps/deskflow-daemon/deskflow-daemon.cpp

@@ -73,6 +73,7 @@ int main(int argc, char **argv)
   // It's important to write the version number to the log file so we can be certain the old daemon
   // was uninstalled, since sometimes Windows services can get stuck and fail to be removed.
   LOG_PRINT("%s v%s", qPrintable(QCoreApplication::applicationName()), kDisplayVersion);
+  LOG_INFO("settings file: %s", qPrintable(Settings::settingsFile()));
 
   // Default log level to system setting (found in Registry).
   auto logLevel = Settings::value(Settings::Daemon::LogLevel).toString().toStdString();

src/lib/deskflow/CMakeLists.txt

@@ -91,6 +91,10 @@ add_library(${lib_name} STATIC ${PLATFORM_CODE}
 
 target_link_libraries(${lib_name} PUBLIC common Qt6::Core Qt6::Network)
 
+if(WIN32)
+  target_link_libraries(${lib_name} PRIVATE platform)
+endif()
+
 if(UNIX)
   target_link_libraries(
     ${lib_name}

src/lib/deskflow/Screen.cpp

@@ -12,8 +12,35 @@
 
 #include <QProcess>
 
+#ifdef Q_OS_WIN
+#include "arch/win32/ArchMiscWindows.h"
+#include "platform/MSWindowsProcess.h"
+#endif
+
 namespace deskflow {
 
+namespace {
+
+bool runScreenCommand(const QString &commandLine)
+{
+#ifdef Q_OS_WIN
+  using deskflow::platform::MSWindowsProcess;
+  if (ArchMiscWindows::isProcessElevated()) {
+    LOG_DEBUG("current process is elevated, starting detached process as session user");
+    return MSWindowsProcess::startDetachedAsSessionUser(commandLine.toStdWString());
+  }
+#endif
+
+  auto args = QProcess::splitCommand(commandLine);
+  if (args.isEmpty()) {
+    return false;
+  }
+  const auto program = args.takeFirst();
+  return QProcess::startDetached(program, args);
+}
+
+} // namespace
+
 //
 // Screen
 //
@@ -123,10 +150,9 @@ void Screen::enter(KeyModifierMask toggleMask)
   }
 
   if (Settings::value(Settings::Core::EnableEnterCommand).toBool()) {
-    auto args = QProcess::splitCommand(Settings::value(Settings::Core::ScreenEnterCommand).toString());
-    const auto command = args.takeFirst();
-    LOG_DEBUG("running screen enter command: %s %s", qPrintable(command), qPrintable(args.join(" ")));
-    if (!QProcess::startDetached(command, args))
+    const auto commandLine = Settings::value(Settings::Core::ScreenEnterCommand).toString();
+    LOG_DEBUG("running screen enter command: %s", qPrintable(commandLine));
+    if (!runScreenCommand(commandLine))
       LOG_ERR("failed to run screen enter command");
   }
 }
@@ -151,10 +177,9 @@ bool Screen::leave()
 
   m_screen->leave();
   if (Settings::value(Settings::Core::EnableExitCommand).toBool()) {
-    auto args = QProcess::splitCommand(Settings::value(Settings::Core::ScreenExitCommand).toString());
-    const auto command = args.takeFirst();
-    LOG_DEBUG("running screen exit command: %s %s", qPrintable(command), qPrintable(args.join(" ")));
-    if (!QProcess::startDetached(command, args))
+    const auto commandLine = Settings::value(Settings::Core::ScreenExitCommand).toString();
+    LOG_DEBUG("running screen exit command: %s", qPrintable(commandLine));
+    if (!runScreenCommand(commandLine))
       LOG_ERR("failed to run screen exit command");
   }
 

src/lib/platform/MSWindowsProcess.cpp

@@ -11,6 +11,7 @@
 #include "base/Log.h"
 #include "common/Constants.h"
 #include "common/ExitCodes.h"
+#include "platform/MSWindowsSession.h"
 
 #define WIN32_LEAN_AND_MEAN
 #include <Windows.h>
@@ -188,6 +189,51 @@ void MSWindowsProcess::shutdown(HANDLE handle, DWORD pid, int timeout)
   }
 }
 
+bool MSWindowsProcess::startDetachedAsSessionUser(const std::wstring &command)
+{
+  MSWindowsSession session;
+  session.updateActiveSession();
+
+  HANDLE userToken = nullptr;
+  try {
+    userToken = session.getUserToken(nullptr);
+  } catch (const std::runtime_error &e) {
+    LOG_ERR("could not get session user token: %s", e.what());
+    return false;
+  }
+
+  LPVOID environment = nullptr;
+  if (!CreateEnvironmentBlock(&environment, userToken, FALSE)) {
+    LOG_ERR("could not create environment block, error: %s", windowsErrorToString(GetLastError()).c_str());
+    CloseHandle(userToken);
+    return false;
+  }
+
+  STARTUPINFOW si = {};
+  si.cb = sizeof(si);
+  PROCESS_INFORMATION pi = {};
+
+  std::wstring mutableCommand = command;
+  const DWORD flags = CREATE_UNICODE_ENVIRONMENT | CREATE_NEW_CONSOLE;
+
+  LOG_DEBUG("starting detached process as session user, command: %s", command.c_str());
+  const BOOL ok = CreateProcessAsUserW(
+      userToken, nullptr, mutableCommand.data(), nullptr, nullptr, FALSE, flags, environment, nullptr, &si, &pi
+  );
+
+  DestroyEnvironmentBlock(environment);
+  CloseHandle(userToken);
+
+  if (!ok) {
+    LOG_ERR("could not start process as session user, error: %s", windowsErrorToString(GetLastError()).c_str());
+    return false;
+  }
+
+  CloseHandle(pi.hProcess);
+  CloseHandle(pi.hThread);
+  return true;
+}
+
 void MSWindowsProcess::createPipes()
 {
   SECURITY_ATTRIBUTES saAttr;

src/lib/platform/MSWindowsProcess.h

@@ -38,6 +38,10 @@ public:
 
   static void shutdown(HANDLE handle, DWORD pid, int timeout = kDefaultShutdownTimeout);
 
+  /// Launch @p command as a detached process under the active console user's token, so the
+  /// child does not inherit the caller's (SYSTEM) privileges.
+  static bool startDetachedAsSessionUser(const std::wstring &command);
+
 private:
   void setStartupInfo(STARTUPINFO &si);
 

src/unittests/deskflow/CMakeLists.txt

@@ -2,7 +2,7 @@
 # SPDX-License-Identifier: MIT
 
 if(WIN32)
-  set(extra_libs version)
+  set(extra_libs platform version)
 endif()
 
 create_test(