The finish_nested_data function in ext/standard/var_unserializer.re in PHP before 5.6.31, 7.0.x before 7.0.21, and 7.1.x before 7.1.7 is prone to a buffer over-read while unserializing untrusted data. Exploitation of this issue can have an unspecified impact on the integrity of PHP. Upstream bug: https://bugs.php.net/bug.php?id=74111
Created php tracking bugs for this issue: Affects: fedora-all [bug 1484840]
This issue happens when untrusted input is deserialized. Doing so is documented as being unsafe: http://php.net/manual/en/function.unserialize.php "Do not pass untrusted user input to unserialize() regardless of the options value of allowed_classes. Unserialization can result in code being loaded and executed due to object instantiation and autoloading, and a malicious user may be able to exploit this. Use a safe, standard data interchange format such as JSON (via json_decode() and json_encode()) if you need to pass serialized data to the user." "If you need to unserialize externally stored serialized data, consider to use hash_hmac() for data validation. Make sure data is not modified by anyone, but you."
This issue has been addressed in the following products: Red Hat Software Collections for Red Hat Enterprise Linux 6 Red Hat Software Collections for Red Hat Enterprise Linux 6.7 EUS Red Hat Software Collections for Red Hat Enterprise Linux 7 Red Hat Software Collections for Red Hat Enterprise Linux 7.3 EUS Red Hat Software Collections for Red Hat Enterprise Linux 7.4 EUS Red Hat Software Collections for Red Hat Enterprise Linux 7.5 EUS Via RHSA-2018:1296 https://access.redhat.com/errata/RHSA-2018:1296