main/streams/xp_socket.c in PHP 7.x before 2017-03-07 misparses fsockopen calls, such as by interpreting fsockopen('127.0.0.1:80', 443) as if the address/port were 127.0.0.1:80:443, which is later truncated to 127.0.0.1:80. This behavior has a security risk if the explicitly provided port number (i.e., 443 in this example) is hardcoded into an application as a security policy, but the hostname argument (i.e., 127.0.0.1:80 in this example) is obtained from untrusted input.

References

• https://nvd.nist.gov/vuln/detail/CVE-2017-7189
• php/php-src@bab0b99
• https://bugs.php.net/bug.php?id=74192