#VU54170 Input validation error in PHPMailer - CVE-2021-34551

Vulnerability identifier: #VU54170

Vulnerability risk: Medium

CVSSv4.0: 7.2 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Green]

CVE-ID: CVE-2021-34551

CWE-ID: CWE-20

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
PHPMailer
Web applications / Other software

Vendor: phpmailer.sourceforge.net

Description

The vulnerability allows a remote attacker to compromise the affected system.

The vulnerability exists due to insufficient validation of user-supplied input within the setLanguage() method when processing the $lang_path parameter on a Windows system. A remote attacker can pass specially crafted input to the application, set a UNC path via the affected parameter and execute arbitrary PHP code on the system.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

PHPMailer: 2.0.3 - 6.4.1

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External links
https://github.com/PHPMailer/PHPMailer/releases/tag/v6.5.0

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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.