CVE-2021-43118 : Security Advisory and Response

A Remote Command Injection vulnerability exists in DrayTek Vigor 2960 1.5.1.3, DrayTek Vigor 3900 1.5.1.3, and DrayTek Vigor 300B 1.5.1.3 via a crafted HTTP message containing malformed QUERY STRING in mainfunction.cgi, which could let a remote malicious user execute arbitrary code.

Understanding CVE-2021-43118

This CVE involves a Remote Command Injection vulnerability in DrayTek Vigor routers that could allow remote attackers to execute arbitrary code.

What is CVE-2021-43118?

CVE-2021-43118 is a Remote Command Injection vulnerability found in DrayTek Vigor routers when processing a specially crafted HTTP message.

The Impact of CVE-2021-43118

The vulnerability can be exploited by a remote malicious user to execute arbitrary code on the affected devices.

Technical Details of CVE-2021-43118

This section provides detailed technical information about the CVE.

Vulnerability Description

The vulnerability exists in DrayTek Vigor 2960 1.5.1.3, DrayTek Vigor 3900 1.5.1.3, and DrayTek Vigor 300B 1.5.1.3 due to a flaw in handling malformed QUERY STRING in mainfunction.cgi.

Affected Systems and Versions

DrayTek Vigor 2960 1.5.1.3
DrayTek Vigor 3900 1.5.1.3
DrayTek Vigor 300B 1.5.1.3

Exploitation Mechanism

The vulnerability can be exploited by sending a specially crafted HTTP message with a malformed QUERY STRING to the mainfunction.cgi script.

Mitigation and Prevention

Steps to address and prevent exploitation of CVE-2021-43118.

Immediate Steps to Take

Update DrayTek Vigor routers to the latest firmware version.
Monitor network traffic for any suspicious activity.
Implement firewall rules to restrict external access to affected devices.

Long-Term Security Practices

Regularly update and patch all network devices.
Conduct security audits and penetration testing on network infrastructure.

Patching and Updates

Vendor-supplied patches should be applied promptly to mitigate the vulnerability.