#VU58331 Input validation error in PHP - CVE-2021-21707

Vulnerability identifier: #VU58331

Vulnerability risk: Medium

CVSSv4.0: 2.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N/E:U/U:Green]

CVE-ID: CVE-2021-21707

CWE-ID: CWE-20

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
PHP
Universal components / Libraries / Scripting languages

Vendor: PHP Group

Description

The vulnerability allows a remote attacker to inject arbitrary XML code.

The vulnerability exists due to insufficient validation of user-supplied input within the simplexml_load_file() PHP function when processing NULL byte character (e.g. %00). A remote attacker can pass specially crafted URL to the application and bypass implemented security restrictions.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

PHP: 7.3 - 7.3.32, 7.4 - 7.4.25, 8.0.0 - 8.0.12

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External links
https://www.php.net/ChangeLog-8.php#8.0.13
https://www.php.net/ChangeLog-7.php#7.4.26
https://www.php.net/ChangeLog-7.php#7.3.33
https://bugs.php.net/bug.php?id=79971

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Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.