#VU57656 Out-of-bounds write in PHP - CVE-2021-21703
Published: October 26, 2021 / Updated: October 27, 2023
Vulnerability identifier: #VU57656
Vulnerability risk: Low
CVSSv4.0: CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:P/U:Clear
CVE-ID: CVE-2021-21703
CWE-ID: CWE-787
Exploitation vector: Local access
Exploit availability:
No public exploit available
Vulnerable software:
PHP
PHP
Software vendor:
PHP Group
PHP Group
Description
The vulnerability allows a local user to escalate privileges on the system.
The vulnerability exists in the way PHP handles shared memory access, when using PHP FPM SAPI with main FPM daemon process running as root and child worker processes running as lower-privileged users. A child process can access shared memory with the main process and write to it. As a result, it is possible to cause the root process to conduct invalid memory reads and writes with root privileges. A local user can trigger an out-of-bounds write error and execute arbitrary code on the system with root privileges.
Remediation
Install updates from vendor's website.