CVE-2021-21703

About vulnerability

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.

Affected product:

Alpine Linux 3.22 , CentOS 6 ELS , CentOS 7 ELS , CentOS 8.4 ELS , CentOS 8.5 ELS , CloudLinux 6 ELS , CloudLinux 7 ELS , Debian 10 , Debian 10 ELS , Debian 11 , Debian 12 , Debian 13 , EL 10 , EL 6 , EL 7 , EL 8 , EL 9 , Oracle Linux 6 ELS , Ubuntu 16.04 , Ubuntu 16.04 ELS , Ubuntu 18.04 , Ubuntu 18.04 ELS , Ubuntu 20.04 , Ubuntu 22.04 , Ubuntu 24.04 , Windows 10

Affected packages:

php @ 5.4 (+175 more)

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.