diff --git a/CHANGELOG.md b/CHANGELOG.md
index b4329a12d..3d1d1a3d9 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,10 @@
 
 * Dropped the PIN database
 
+### Bugs fixed
+
+* blueman-mechanism accepted arbitrary file paths and returned the errors from trying to open them, see https://github.com/blueman-project/blueman/security/advisories/GHSA-3r9p-m5c8-8mw8
+
 ## 2.2.3
 
 ### Bugs fixed
diff --git a/blueman/plugins/applet/PPPSupport.py b/blueman/plugins/applet/PPPSupport.py
index 5130121fc..8af2811b4 100644
--- a/blueman/plugins/applet/PPPSupport.py
+++ b/blueman/plugins/applet/PPPSupport.py
@@ -28,7 +28,7 @@ def on_ppp_connected(self, device: Device, rfcomm: str, ppp_port: str) -> None:
 
 
 class Connection:
-    def __init__(self, applet: "BluemanApplet", service: DialupNetwork, port: str,
+    def __init__(self, applet: "BluemanApplet", service: DialupNetwork, port: int,
                  ok: Callable[[str], None], err: Callable[[GLib.Error], None]):
         self.reply_handler = ok
         self.error_handler = err
@@ -48,26 +48,26 @@ def connect(self) -> bool:
         c = Config("org.blueman.gsmsetting", f"/org/blueman/gsmsettings/{self.service.device['Address']}/")
 
         m = Mechanism()
-        m.PPPConnect('(sss)', self.port, c["number"], c["apn"], result_handler=self.on_connected,
+        m.PPPConnect('(uss)', self.port, c["number"], c["apn"], result_handler=self.on_connected,
                      error_handler=self.on_error)
 
         return False
 
     def on_error(self, _obj: Mechanism, result: GLib.Error, _user_data: None) -> None:
         logging.info(f"Failed {result}")
-        # FIXME confusingly self.port is the full rfcomm device path but the service expects the number only
         self.error_handler(result)
 
         def _connect() -> bool:
-            self.service.disconnect(int(self.port[-1]))
+            self.service.disconnect(self.port)
             return False
 
         GLib.timeout_add(1000, _connect)
 
     def on_connected(self, _obj: Mechanism, result: str, _user_data: None) -> None:
-        self.reply_handler(self.port)
+        rfcomm_dev = f"/dev/rfcomm{self.port:d}"
+        self.reply_handler(rfcomm_dev)
         for plugin in self.parent.Plugins.get_loaded_plugins(PPPConnectedListener):
-            plugin.on_ppp_connected(self.service.device, self.port, result)
+            plugin.on_ppp_connected(self.service.device, rfcomm_dev, result)
 
         msg = _("Successfully connected to <b>DUN</b> service on <b>%(0)s.</b>\n"
                 "Network is now available through <b>%(1)s</b>") % {"0": self.service.device['Alias'], "1": result}
@@ -85,7 +85,7 @@ class PPPSupport(AppletPlugin, RFCOMMConnectHandler):
     def rfcomm_connect_handler(self, service: SerialService, reply: Callable[[str], None],
                                err: Callable[[Union[RFCOMMError, GLib.Error]], None]) -> bool:
         if isinstance(service, DialupNetwork):
-            def local_reply(port: str) -> None:
+            def local_reply(port: int) -> None:
                 assert isinstance(service, DialupNetwork)  # https://github.com/python/mypy/issues/2608
                 Connection(self.parent, service, port, reply, err)
 
diff --git a/blueman/plugins/mechanism/Ppp.py b/blueman/plugins/mechanism/Ppp.py
index a9e31aa1c..25d5a592e 100644
--- a/blueman/plugins/mechanism/Ppp.py
+++ b/blueman/plugins/mechanism/Ppp.py
@@ -6,7 +6,7 @@
 
 class Ppp(MechanismPlugin):
     def on_load(self) -> None:
-        self.parent.add_method("PPPConnect", ("s", "s", "s"), "s", self._ppp_connect, pass_sender=True, is_async=True)
+        self.parent.add_method("PPPConnect", ("u", "s", "s"), "s", self._ppp_connect, pass_sender=True, is_async=True)
 
     def _ppp_connected(self, _ppp: PPPConnection, port: str, ok: Callable[[str], None]) -> None:
         ok(port)
@@ -16,12 +16,12 @@ def _ppp_error(self, _ppp: PPPConnection, message: str, err: Callable[[str], Non
         err(message)
         self.timer.resume()
 
-    def _ppp_connect(self, port: str, number: str, apn: str, caller: str,
+    def _ppp_connect(self, port: int, number: str, apn: str, caller: str,
                      ok: Callable[[str], None], err: Callable[[str], None]) -> None:
         self.confirm_authorization(caller, "org.blueman.pppd.pppconnect")
         self.timer.stop()
 
-        ppp = PPPConnection(port, number, apn)
+        ppp = PPPConnection(f"/dev/rfcomm{port:d}", number, apn)
         ppp.connect("error-occurred", self._ppp_error, err)
         ppp.connect("connected", self._ppp_connected, ok)
 
diff --git a/blueman/services/meta/SerialService.py b/blueman/services/meta/SerialService.py
index 4195306da..28f84f9c3 100644
--- a/blueman/services/meta/SerialService.py
+++ b/blueman/services/meta/SerialService.py
@@ -70,7 +70,7 @@ def try_replace_root_watcher(self, monitor: Gio.FileMonitor, path: str, port: in
 
     def connect(
         self,
-        reply_handler: Optional[Callable[[str], None]] = None,
+        reply_handler: Optional[Callable[[int], None]] = None,
         error_handler: Optional[Callable[[RFCOMMError], None]] = None
     ) -> bool:
         # We expect this service to have a reserved UUID
@@ -96,7 +96,7 @@ def connect(
             self.try_replace_root_watcher(mon, filename, port_id)
 
             if reply_handler:
-                reply_handler(filename)
+                reply_handler(port_id)
         except RFCOMMError as e:
             if error_handler:
                 error_handler(e)