CVE-2021-21707

Description

In PHP versions 7.3.x below 7.3.33, 7.4.x below 7.4.26 and 8.0.x below 8.0.13, certain XML parsing functions, like simplexml_load_file(), URL-decode the filename passed to them. If that filename contains URL-encoded NUL character, this may cause the function to interpret this as the end of the filename, thus interpreting the filename differently from what the user intended, which may lead it to reading a different file than intended.

How to fix CVE-2021-21707

To remediate CVE-2021-21707, upgrade the affected package to a fixed version below.

—upgrade to 7.3.33 or later
—upgrade to 7.3.33 or later
—upgrade to 7.3.33 or later
—upgrade to 7.3.31-1~deb10u2 or later
—upgrade to 7.4.28-1+deb11u1 or later
—upgrade to 7.4.28-1+deb11u1 or later

Is CVE-2021-21707 being exploited?

Low — EPSS is 0.6%, meaning exploitation activity has not been observed at scale.

Affected packages (6)

>= 7.3.0, < 7.3.33, >= 7.4.0, < 7.4.26, >= 8.0.0, < 8.0.13
>= 7.3.0, < 7.3.33, >= 7.4.0, < 7.4.26, >= 8.0.0, < 8.0.13
>= 7.3.0, < 7.3.33, >= 7.4.0, < 7.4.26, >= 8.0.0, < 8.0.13
from 0, < 7.3.31-1~deb10u2
from 0, < 7.4.28-1+deb11u1
from 0, < 7.4.28-1+deb11u1

CVSS scores

Source	Version	Severity	Vector
osv	CVSS 3.1	MEDIUM5.3	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N