The pointer returned by php_stream_fopen_tmpfile is not validated prior to use in memory.c.
In the case where a script is executed in an environment where the parent directory of system TMP directory is not readable to the user, it will cause a application crash with Access Violation.

The issue is similar to the https://bugs.php.net/bug.php?id=68986

Steps to reproduce:

1. Create C:\TEMP folder
2. Create system user
3. Add Deny Full control access rights for created user on C:\
4. Remove Deny Full control access rights for created user on C:\TEMP
5. Add Allow Full control access rights for created user on C:\TEMP
6. Set TEMP and TMP system environment variables value to C:\TEMP
7. Execute script by created user:

<?php
$fp = fopen('php://temp', 'w+b');
$ch = curl_init();
curl_setopt($ch, CURLOPT_FILE, $fp);