diff --git a/vncviewer/CConn.cxx b/vncviewer/CConn.cxx
index 12ebbe4..405cd97 100644
--- a/vncviewer/CConn.cxx
+++ b/vncviewer/CConn.cxx
@@ -99,7 +99,7 @@
     sock = new network::TcpSocket(serverHost, serverPort);
     vlog.info(_("connected to host %s port %d"), serverHost, serverPort);
   } catch (rdr::Exception& e) {
-    vlog.error(e.str());
+    vlog.error("%s", e.str());
     fl_alert("%s", e.str());
     exit_vncviewer();
     return;
@@ -210,10 +210,10 @@
       cc->processMsg();
     } while (cc->sock->inStream().checkNoWait(1));
   } catch (rdr::EndOfStream& e) {
-    vlog.info(e.str());
+    vlog.info("%s", e.str());
     exit_vncviewer();
   } catch (rdr::Exception& e) {
-    vlog.error(e.str());
+    vlog.error("%s", e.str());
     exit_vncviewer(e.str());
   }
 
diff --git a/vncviewer/Viewport.cxx b/vncviewer/Viewport.cxx
index 1588f27..65dcfb2 100644
--- a/vncviewer/Viewport.cxx
+++ b/vncviewer/Viewport.cxx
@@ -369,7 +369,7 @@
     try {
       cc->writer()->clientCutText(buffer, ret);
     } catch (rdr::Exception& e) {
-      vlog.error(e.str());
+      vlog.error("%s", e.str());
       exit_vncviewer(e.str());
     }
 
@@ -501,7 +501,7 @@
       try {
         cc->writer()->pointerEvent(pos, buttonMask);
       } catch (rdr::Exception& e) {
-        vlog.error(e.str());
+        vlog.error("%s", e.str());
         exit_vncviewer(e.str());
       }
     } else {
@@ -524,7 +524,7 @@
   try {
     self->cc->writer()->pointerEvent(self->lastPointerPos, self->lastButtonMask);
   } catch (rdr::Exception& e) {
-    vlog.error(e.str());
+    vlog.error("%s", e.str());
     exit_vncviewer(e.str());
   }
 }
@@ -756,7 +756,7 @@
     try {
       cc->writer()->keyEvent(iter->second, false);
     } catch (rdr::Exception& e) {
-      vlog.error(e.str());
+      vlog.error("%s", e.str());
       exit_vncviewer(e.str());
     }
 
@@ -800,7 +800,7 @@
       if (downKeySym.find(FL_Alt_R) != downKeySym.end())
         cc->writer()->keyEvent(XK_Alt_R, false);
     } catch (rdr::Exception& e) {
-      vlog.error(e.str());
+      vlog.error("%s", e.str());
       exit_vncviewer(e.str());
     }
   }
@@ -814,7 +814,7 @@
   try {
     cc->writer()->keyEvent(keySym, down);
   } catch (rdr::Exception& e) {
-    vlog.error(e.str());
+    vlog.error("%s", e.str());
     exit_vncviewer(e.str());
   }