D-Link DNS Series Command Injection via /cgi-bin/App_Mgr.cgi (FTP_BlockIP)
CVE-2026-4205 Published on March 16, 2026

D-Link DNS-1550-04 app_mgr.cgi FTP_Server_BlockIP_Del command injection
A vulnerability has been found in D-Link DNS-120, DNR-202L, DNS-315L, DNS-320, DNS-320L, DNS-320LW, DNS-321, DNR-322L, DNS-323, DNS-325, DNS-326, DNS-327L, DNR-326, DNS-340L, DNS-343, DNS-345, DNS-726-4, DNS-1100-4, DNS-1200-05 and DNS-1550-04 up to 20260205. The impacted element is the function cgi_refresh_db/FTP_Server_BlockIP_Add/FTP_Server_BlockIP_Del of the file /cgi-bin/app_mgr.cgi. Such manipulation leads to command injection. The attack can be executed remotely. The exploit has been disclosed to the public and may be used.

NVD

Timeline

Advisory disclosed

VulDB entry created

VulDB entry last update

Weakness Types

What is a Command Injection Vulnerability?

The software 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.

CVE-2026-4205 has been classified to as a Command Injection vulnerability or weakness.

What is an Injection Vulnerability?

The software constructs all or part of a command, data structure, or record using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify how it is parsed or interpreted when it is sent to a downstream component. Software has certain assumptions about what constitutes data and control respectively. It is the lack of verification of these assumptions for user-controlled input that leads to injection problems. Injection problems encompass a wide variety of issues -- all mitigated in very different ways and usually attempted in order to alter the control flow of the process. For this reason, the most effective way to discuss these weaknesses is to note the distinct features which classify them as injection weaknesses. The most important issue to note is that all injection problems share one thing in common -- i.e., they allow for the injection of control plane data into the user-controlled data plane. This means that the execution of the process may be altered by sending code in through legitimate data channels, using no other mechanism. While buffer overflows, and many other flaws, involve the use of some further issue to gain execution, injection problems need only for the data to be parsed. The most classic instantiations of this category of weakness are SQL injection and format string vulnerabilities.

CVE-2026-4205 has been classified to as an Injection vulnerability or weakness.


Affected Versions

D-Link DNS-120: D-Link DNR-202L: D-Link DNS-315L: D-Link DNS-320: D-Link DNS-320L: D-Link DNS-320LW: D-Link DNS-321: D-Link DNR-322L: D-Link DNS-323: D-Link DNS-325: D-Link DNS-326: D-Link DNS-327L: D-Link DNR-326: D-Link DNS-340L: D-Link DNS-343: D-Link DNS-345: D-Link DNS-726-4: D-Link DNS-1100-4: D-Link DNS-1200-05: D-Link DNS-1550-04: