--- cyrus-imapd-2.4.19/lib/util.c.orig	2017-05-15 07:43:30.000000000 +0200
+++ cyrus-imapd-2.4.19/lib/util.c	2017-05-17 15:08:09.000000000 +0200
@@ -360,23 +360,36 @@
  */
 int cyrus_mkdir(const char *path, mode_t mode __attribute__((unused)))
 {
-    char *p = (char *) path;
+    char *p, *npath;
     int save_errno;
     struct stat sbuf;
 
-    while ((p = strchr(p+1, '/'))) {
+    /* work with a copy */
+    npath = xstrdup(path);
+
+    /* skip leading slashes */
+    p = npath;
+    while (*p == '/')
+	p++;
+
+    while ((p = strchr(p, '/'))) {
 	*p = '\0';
-	if (mkdir(path, 0755) == -1 && errno != EEXIST) {
+	if (mkdir(npath, 0755) == -1 && errno != EEXIST) {
 	    save_errno = errno;
-	    if (stat(path, &sbuf) == -1) {
+	    if (stat(npath, &sbuf) == -1) {
 		errno = save_errno;
-		syslog(LOG_ERR, "IOERROR: creating directory %s: %m", path);
+		syslog(LOG_ERR, "IOERROR: creating directory %s: %m", npath);
+		free (npath);
 		return -1;
 	    }
 	}
-	*p = '/';
+	/* restore slash and skip multiple following slashes */
+	*p++ = '/';
+	while (*p == '/')
+	    p++;
     }
 
+    free (npath);
     return 0;
 }