diff --git a/src/XrdSecgsi/XrdSecProtocolgsi.cc b/src/XrdSecgsi/XrdSecProtocolgsi.cc
index eab40af561d..31cf001a4af 100644
--- a/src/XrdSecgsi/XrdSecProtocolgsi.cc
+++ b/src/XrdSecgsi/XrdSecProtocolgsi.cc
@@ -3781,7 +3781,7 @@ void XrdSecProtocolgsi::ErrF(XrdOucErrInfo *einfo, kXR_int32 ecode,
       if (bout) {
          bout[0] = 0;
          for (k = 0; k < i; k++)
-            sprintf(bout,"%s%s",bout,msgv[k]);
+            strcat(bout, msgv[k]);
          DEBUG(bout);
       } else {
          for (k = 0; k < i; k++)
diff --git a/src/XrdSecpwd/XrdSecProtocolpwd.cc b/src/XrdSecpwd/XrdSecProtocolpwd.cc
index b067abcb864..b2250dfc009 100644
--- a/src/XrdSecpwd/XrdSecProtocolpwd.cc
+++ b/src/XrdSecpwd/XrdSecProtocolpwd.cc
@@ -3400,7 +3400,7 @@ void XrdSecProtocolpwd::ErrF(XrdOucErrInfo *einfo, kXR_int32 ecode,
       if (bout) {
          bout[0] = 0;
          for (k = 0; k < i; k++)
-            sprintf(bout,"%s%s",bout,msgv[k]);
+            strcat(bout, msgv[k]);
          PRINT(bout);
       } else {
          for (k = 0; k < i; k++)
diff --git a/src/XrdSut/XrdSutAux.cc b/src/XrdSut/XrdSutAux.cc
index cc0723c6e1a..499f2e5d2c6 100644
--- a/src/XrdSut/XrdSutAux.cc
+++ b/src/XrdSut/XrdSutAux.cc
@@ -255,7 +255,11 @@ int XrdSutToHex(const char *in, int lin, char *out)
    int i = 0;
    out[0] = 0;
    for ( ; i < lin; i++)
-      sprintf(out,"%s%02x",out,(0xFF & in[i]));
+   {
+      char buff[3];
+      sprintf(buff, "%02x", (0xFF & in[i]));
+      strncat(out, buff, 3);
+   }
    // Null termination
    out[lbuf-1] = 0;