CVE-2013-2174: Heap-based buffer overflow in the curl_easy_unescape function
in lib/escape.c in cURL and libcurl 7.7 through 7.30.0 allows remote
attackers to cause a denial of service (application crash) or possibly
execute arbitrary code via a crafted string ending in a "%" (percent)
character.

CVE webpage for this problem:
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2013-2174

Relevant upstream patch at:
https://github.com/bagder/curl/commit/192c4f788d48f82c03e9cef40013f34370e90737

--- lib/escape.c.orig	2013-08-20 17:09:51.197431224 -0700
+++ lib/escape.c	2013-08-20 17:10:43.746809478 -0700
@@ -5,7 +5,7 @@
  *                            | (__| |_| |  _ <| |___
  *                             \___|\___/|_| \_\_____|
  *
- * Copyright (C) 1998 - 2011, Daniel Stenberg, <[email protected]>, et al.
+ * Copyright (C) 1998 - 2013, Daniel Stenberg, <[email protected]>, et al.
  *
  * This software is licensed as described in the file COPYING, which
  * you should have received as part of this distribution. The terms
@@ -159,7 +159,8 @@
 
   while(--alloc > 0) {
     in = *string;
-    if(('%' == in) && ISXDIGIT(string[1]) && ISXDIGIT(string[2])) {
+    if(('%' == in) && (alloc > 2) &&
+       ISXDIGIT(string[1]) && ISXDIGIT(string[2])) {
       /* this is two hexadecimal digits following a '%' */
       char hexstr[3];
       char *ptr;