#VU25350 Improper Neutralization of Special Elements in Output Used by a Downstream Component in DrayTek Corp. products - CVE-2020-8515

Vulnerability identifier: #VU25350

Vulnerability risk: Critical

CVSSv4.0: 9.3 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:A/U:Red]

CVE-ID: CVE-2020-8515

CWE-ID: CWE-74

Exploitation vector: Network

Exploit availability: Yes

Vulnerable software:
Vigor 2960
Hardware solutions / Routers & switches, VoIP, GSM, etc
Vigor 3900
Hardware solutions / Routers & switches, VoIP, GSM, etc
Vigor 300B
Hardware solutions / Routers & switches, VoIP, GSM, etc

Vendor: DrayTek Corp.

Description

The vulnerability allows a remote attacker to execute arbitrary code on the target system.

The vulnerability exists due to the affected devices allow remote code execution as root (without authentication) via shell metacharacters to the "cgi-bin/mainfunction.cgi" URI.

Note, this vulnerability is being actively exploited in the wild starting from December 4, 2019.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

Vigor 2960: 1.3.1 _

Vigor 3900: 1.4.4 _

Vigor 300B: 1.3.3 _ - 1.4.4 _

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External links
https://sku11army.blogspot.com/2020/01/draytek-unauthenticated-rce-in-draytek.html
https://www.draytek.com/about/security-advisory/vigor3900-/-vigor2960-/-vigor300b-router-web-management-page-vulnerability-(cve-2020-8515)/
https://blog.netlab.360.com/two-zero-days-are-targeting-draytek-broadband-cpe-devices-en/

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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?

Yes. This vulnerability is being exploited in the wild.