CVE-2021-21703

In PHP versions 7.3.x up to and including 7.3.31, 7.4.x below 7.4.25 and
8.0.x below 8.0.12, when running PHP FPM SAPI with main FPM daemon process
running as root and child worker processes running as lower-privileged
users, it is possible for the child processes to access memory shared with
the main process and write to it, modifying it in a way that would cause
the root process to conduct invalid memory reads and writes, which can be
used to escalate privileges from local unprivileged user to the root user.

Bugs

• <https://bugs.php.net/bug.php?id=81026&gt;

Notes