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.
https://bugs.php.net/bug.php?id=81026
https://www.debian.org/security/2021/dsa-4993
https://www.debian.org/security/2021/dsa-4992
http://www.openwall.com/lists/oss-security/2021/10/26/7
https://lists.debian.org/debian-lts-announce/2021/10/msg00021.html
https://security.netapp.com/advisory/ntap-20211118-0003/
https://www.oracle.com/security-alerts/cpujan2022.html
Source: MITRE
Published: 2021-10-25
Updated: 2022-10-29
Type: CWE-787
Base Score: 6.9
Vector: AV:L/AC:M/Au:N/C:C/I:C/A:C
Impact Score: 10
Exploitability Score: 3.4
Severity: MEDIUM
Base Score: 7
Vector: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Impact Score: 5.9
Exploitability Score: 1
Severity: HIGH