CVE-2021-21703

Description

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.

How to fix CVE-2021-21703

To remediate CVE-2021-21703, upgrade the affected package to a fixed version below.

—upgrade to 7.3.32 or later
—upgrade to 7.3.32 or later
—upgrade to 7.3.32 or later
—upgrade to 7.0.33-0+deb9u12 or later
—upgrade to 7.3.31-1~deb10u1 or later
—upgrade to 7.4.25-1+deb11u1 or later
—upgrade to 7.4.25-1+deb11u1 or later

Is CVE-2021-21703 being exploited?

Low — EPSS is 0.1%, meaning exploitation activity has not been observed at scale.

Affected packages (7)

>= 7.3.0, < 7.3.32, >= 7.4.0, < 7.4.25, >= 8.0.0, < 8.0.12
>= 7.3.0, < 7.3.32, >= 7.4.0, < 7.4.25, >= 8.0.0, < 8.0.12
>= 7.3.0, < 7.3.32, >= 7.4.0, < 7.4.25, >= 8.0.0, < 8.0.12
from 0, < 7.0.33-0+deb9u12
from 0, < 7.3.31-1~deb10u1
from 0, < 7.4.25-1+deb11u1
from 0, < 7.4.25-1+deb11u1

CVSS scores

Source	Version	Severity	Vector
osv	CVSS 3.1	HIGH7.0	CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H