diff --git a/nixos/modules/security/polkit.nix b/nixos/modules/security/polkit.nix
index ca0a88246528..d4a99ba8a7b6 100644
--- a/nixos/modules/security/polkit.nix
+++ b/nixos/modules/security/polkit.nix
@@ -80,6 +80,28 @@ in
 
     systemd.sockets."polkit-agent-helper".wantedBy = [ "sockets.target" ];
 
+    systemd.services."polkit-agent-helper@".serviceConfig = lib.mkMerge [
+      # The upstream unit inherits stderr to the polkit agent, which causes
+      # agent processes to misinterpret diagnostic output from PAM modules
+      # as protocol errors, resulting in tight re-execution loops.
+      { StandardError = "journal"; }
+
+      # The upstream unit uses PrivateDevices=yes and ProtectHome=yes,
+      # which prevents PAM modules from accessing hardware (e.g. FIDO
+      # tokens via /dev/hidraw*) or reading key files from home directories.
+      (lib.mkIf config.security.pam.u2f.enable {
+        # Override upstream PrivateDevices=yes to allow access to /dev/hidraw*
+        PrivateDevices = false;
+        DeviceAllow = [
+          "/dev/urandom r"
+          "char-hidraw rw"
+        ];
+        # Override upstream ProtectHome=yes so pam_u2f can read
+        # ~/.config/Yubico/u2f_keys (the default key file location)
+        ProtectHome = "read-only";
+      })
+    ];
+
     # The polkit daemon reads action/rule files
     environment.pathsToLink = [ "/share/polkit-1" ];