Vulnerability identifier: #VU56905

Vulnerability risk: Medium

CVSSv3.1: 6.4 [CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N/E:U/RL:O/RC:C]

CVE-ID: CVE-2021-21706

CWE-ID: CWE-36

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
PHP
Universal components / Libraries / Scripting languages

Vendor: PHP Group

Description

The vulnerability allows a remote attacker overwrite files on the system.

The vulnerability exists due to insufficient filtration of file names in the php_zip_make_relative_path() function on Windows systems. A remote attacker can construct a specially crafted ZIP archive, which once extracted by the ZipArchive::extractTo() function, can overwrite files outside of the destination directory.

Successful exploitation of the vulnerability may allow an attacker to overwrite arbitrary files on the system with privileges of the web server, but requires that the web application is running on Windows.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

PHP: 7.4 - 7.4.23, 7.3 - 7.3.30, 8.0.0 - 8.0.10

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External links
http://www.php.net/ChangeLog-7.php#7.4.24
http://bugs.php.net/bug.php?id=81420
http://www.php.net/ChangeLog-7.php#7.3.31

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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.