Netis NC21 4.0.1.4296 HTTP POST Request /cgi-bin/skk_set.cgi password/new_pwd_confirm command injection

Summaryinfo

A vulnerability identified as critical has been detected in Netis NC21 4.0.1.4296. This affects an unknown function of the file /cgi-bin/skk_set.cgi of the component HTTP POST Request Handler. Performing a manipulation of the argument password/new_pwd_confirm results in command injection. This vulnerability is known as CVE-2026-36540. Remote exploitation of the attack is possible. No exploit is available.

Detailsinfo

A vulnerability classified as very critical has been found in Netis NC21 4.0.1.4296. This affects some unknown functionality of the file /cgi-bin/skk_set.cgi of the component HTTP POST Request Handler. The manipulation of the argument password/new_pwd_confirm with an unknown input leads to a command injection vulnerability. CWE is classifying the issue as CWE-77. The product constructs all or part of a command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended command when it is sent to a downstream component. This is going to have an impact on confidentiality, integrity, and availability. The summary by CVE is:

Netis AC1200 Router NC21 V4.0.1.4296 is vulnerable to unauthenticated command injection via the /cgi-bin/skk_set.cgi endpoint. The password and new_pwd_confirm POST parameters are passed directly to the underlying OS shell without sanitization. An attacker can inject arbitrary shell commands by wrapping them in backticks (`) and encoding them in base64. Because the endpoint requires no authentication, any device on the LAN can achieve full Remote Code Execution on the router's operating system with a single HTTP POST request.

This vulnerability is uniquely identified as CVE-2026-36540 since 04/06/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. Technical details are known, but no exploit is available. The price for an exploit might be around USD $0-$5k at the moment (estimation calculated on 05/27/2026). MITRE ATT&CK project uses the attack technique T1202 for this issue.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

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Productinfo

Vendor

• Netis

Name

• NC21

Version

• 4.0.1.4296

CPE 2.3info

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CPE 2.2info

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