diff -urNad proftpd-dfsg-1.3.0~/src/auth.c proftpd-dfsg-1.3.0/src/auth.c
--- proftpd-dfsg-1.3.0~/src/auth.c	2007-04-17 23:38:06.000000000 +0200
+++ proftpd-dfsg-1.3.0/src/auth.c	2007-04-17 23:38:50.000000000 +0200
@@ -64,27 +64,38 @@
 }
 
 static modret_t *dispatch_auth(cmd_rec *cmd, char *match) {
-  authtable *authtab = NULL;
+  authtable *start_tab = NULL, *iter_tab = NULL;
   modret_t *mr = NULL;
 
-  authtab = pr_stash_get_symbol(PR_SYM_AUTH, match, NULL,
+  start_tab = pr_stash_get_symbol(PR_SYM_AUTH, match, NULL,
     &cmd->stash_index);
+  iter_tab = start_tab;
+
+  while (iter_tab) {
+    pr_signals_handle();
 
-  while (authtab) {
     pr_log_debug(DEBUG6, "dispatching auth request \"%s\" to module mod_%s",
-      match, authtab->m->name);
+      match, iter_tab->m->name);
 
-    mr = call_module(authtab->m, authtab->handler, cmd);
+    mr = call_module(iter_tab->m, iter_tab->handler, cmd);
 
-    if (authtab->auth_flags & PR_AUTH_FL_REQUIRED)
+    if (iter_tab->auth_flags & PR_AUTH_FL_REQUIRED)
       break;
 
     if (MODRET_ISHANDLED(mr) ||
         MODRET_ISERROR(mr))
       break;
 
-    authtab = pr_stash_get_symbol(PR_SYM_AUTH, match, authtab,
+    iter_tab = pr_stash_get_symbol(PR_SYM_AUTH, match, iter_tab,
       &cmd->stash_index);
+ 
+     if (iter_tab == start_tab) {
+       /* We have looped back to the start.  Break out now and do not loop
+        * around again (and again, and again...)
+        */
+       mr = PR_DECLINED(cmd);
+       break;
+     }
   }
 
   return mr;