diff --git a/r5dev/thirdparty/curl/curl_ntlm_core.c b/r5dev/thirdparty/curl/curl_ntlm_core.c
index fb43dda1..d5631a72 100644
--- a/r5dev/thirdparty/curl/curl_ntlm_core.c
+++ b/r5dev/thirdparty/curl/curl_ntlm_core.c
@@ -618,6 +618,12 @@ CURLcode Curl_hmac_md5(const unsigned char *key, unsigned int keylen,
   return CURLE_OK;
 }
 
+#if defined(SIZEOF_SIZE_T) && (SIZEOF_SIZE_T > 4)
+#define SIZE_T_MAX 18446744073709551615U
+#else
+#define SIZE_T_MAX 4294967295U
+#endif
+
 /* This creates the NTLMv2 hash by using NTLM hash as the key and Unicode
  * (uppercase UserName + Domain) as the data
  */
@@ -627,10 +633,20 @@ CURLcode Curl_ntlm_core_mk_ntlmv2_hash(const char *user, size_t userlen,
                                        unsigned char *ntlmv2hash)
 {
   /* Unicode representation */
-  size_t identity_len = (userlen + domlen) * 2;
-  unsigned char *identity = malloc(identity_len);
+  size_t identity_len;
+  unsigned char *identity;
   CURLcode result = CURLE_OK;
 
+    /* we do the length checks below separately to avoid integer overflow risk
+     on extreme data lengths */
+  if((userlen > SIZE_T_MAX/2) ||
+     (domlen > SIZE_T_MAX/2) ||
+     ((userlen + domlen) > SIZE_T_MAX/2))
+    return CURLE_OUT_OF_MEMORY;
+
+  identity_len = (userlen + domlen) * 2;
+  identity = malloc(identity_len);
+
   if(!identity)
     return CURLE_OUT_OF_MEMORY;