diff --git a/src/core/ngx_string.c b/src/core/ngx_string.c
index c0bcc1d12..3456baa5c 100644
--- a/src/core/ngx_string.c
+++ b/src/core/ngx_string.c
@@ -819,6 +819,37 @@ ngx_memn2cmp(u_char *s1, u_char *s2, size_t n1, size_t n2)
 }
 
 
+ngx_int_t
+ngx_dns_strcmp(u_char *s1, u_char *s2)
+{
+    ngx_uint_t  c1, c2;
+
+    for ( ;; ) {
+        c1 = (ngx_uint_t) *s1++;
+        c2 = (ngx_uint_t) *s2++;
+
+        c1 = (c1 >= 'A' && c1 <= 'Z') ? (c1 | 0x20) : c1;
+        c2 = (c2 >= 'A' && c2 <= 'Z') ? (c2 | 0x20) : c2;
+
+        if (c1 == c2) {
+
+            if (c1) {
+                continue;
+            }
+
+            return 0;
+        }
+
+        /* in ASCII '.' > '-', but we need '.' to be the lowest character */
+
+        c1 = (c1 == '.') ? ' ' : c1;
+        c2 = (c2 == '.') ? ' ' : c2;
+
+        return c1 - c2;
+    }
+}
+
+
 ngx_int_t
 ngx_atoi(u_char *line, size_t n)
 {
diff --git a/src/core/ngx_string.h b/src/core/ngx_string.h
index 81e1ea169..0525b0e24 100644
--- a/src/core/ngx_string.h
+++ b/src/core/ngx_string.h
@@ -158,6 +158,7 @@ u_char *ngx_strlcasestrn(u_char *s1, u_char *last, u_char *s2, size_t n);
 ngx_int_t ngx_rstrncmp(u_char *s1, u_char *s2, size_t n);
 ngx_int_t ngx_rstrncasecmp(u_char *s1, u_char *s2, size_t n);
 ngx_int_t ngx_memn2cmp(u_char *s1, u_char *s2, size_t n1, size_t n2);
+ngx_int_t ngx_dns_strcmp(u_char *s1, u_char *s2);
 
 ngx_int_t ngx_atoi(u_char *line, size_t n);
 ssize_t ngx_atosz(u_char *line, size_t n);
diff --git a/src/http/modules/ngx_http_map_module.c b/src/http/modules/ngx_http_map_module.c
index 1f7786c3c..abdae0d3b 100644
--- a/src/http/modules/ngx_http_map_module.c
+++ b/src/http/modules/ngx_http_map_module.c
@@ -337,7 +337,7 @@ ngx_http_map_cmp_dns_wildcards(const void *one, const void *two)
     first = (ngx_hash_key_t *) one;
     second = (ngx_hash_key_t *) two;
 
-    return ngx_strcmp(first->key.data, second->key.data);
+    return ngx_dns_strcmp(first->key.data, second->key.data);
 }
 
 
diff --git a/src/http/modules/ngx_http_referer_module.c b/src/http/modules/ngx_http_referer_module.c
index 658f4a19c..8daa399bd 100644
--- a/src/http/modules/ngx_http_referer_module.c
+++ b/src/http/modules/ngx_http_referer_module.c
@@ -506,6 +506,11 @@ ngx_http_add_regex_referer(ngx_conf_t *cf, ngx_http_referer_conf_t *rlcf,
     ngx_regex_elt_t  *re;
     u_char            errstr[NGX_MAX_CONF_ERRSTR];
 
+    if (name->len == 1) {
+        ngx_conf_log_error(NGX_LOG_EMERG, cf, 0, "empty regex in \"%V\"", name);
+        return NGX_CONF_ERROR;
+    }
+
     if (rlcf->regex == NGX_CONF_UNSET_PTR) {
         rlcf->regex = ngx_array_create(cf->pool, 2, sizeof(ngx_regex_elt_t));
         if (rlcf->regex == NULL) {
@@ -562,5 +567,5 @@ ngx_http_cmp_referer_wildcards(const void *one, const void *two)
     first = (ngx_hash_key_t *) one;
     second = (ngx_hash_key_t *) two;
 
-    return ngx_strcmp(first->key.data, second->key.data);
+    return ngx_dns_strcmp(first->key.data, second->key.data);
 }
diff --git a/src/http/ngx_http.c b/src/http/ngx_http.c
index b0915157c..f5cb430fa 100644
--- a/src/http/ngx_http.c
+++ b/src/http/ngx_http.c
@@ -1601,7 +1601,7 @@ ngx_http_cmp_dns_wildcards(const void *one, const void *two)
     first = (ngx_hash_key_t *) one;
     second = (ngx_hash_key_t *) two;
 
-    return ngx_strcmp(first->key.data, second->key.data);
+    return ngx_dns_strcmp(first->key.data, second->key.data);
 }
 
 
diff --git a/src/http/ngx_http_core_module.c b/src/http/ngx_http_core_module.c
index 799dfc856..01e4da397 100644
--- a/src/http/ngx_http_core_module.c
+++ b/src/http/ngx_http_core_module.c
@@ -3512,6 +3512,12 @@ ngx_http_core_server_name(ngx_conf_t *cf, ngx_command_t *cmd, void *conf)
         ngx_str_t  err;
         u_char     errstr[NGX_MAX_CONF_ERRSTR];
 
+        if (value[i].len == 1) {
+            ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
+                               "empty regex in server name \"%V\"", &value[i]);
+            return NGX_CONF_ERROR;
+        }
+
         err.len = NGX_MAX_CONF_ERRSTR;
         err.data = errstr;
 
diff --git a/src/http/ngx_http_request.c b/src/http/ngx_http_request.c
index 13b069226..541d305ec 100644
--- a/src/http/ngx_http_request.c
+++ b/src/http/ngx_http_request.c
@@ -1658,7 +1658,7 @@ ngx_http_find_virtual_server(ngx_http_request_t *r, u_char *host, size_t len)
 
 #if (NGX_PCRE)
 
-    if (r->virtual_names->nregex) {
+    if (len && r->virtual_names->nregex) {
         size_t                   ncaptures;
         ngx_int_t                n;
         ngx_uint_t               i;