VulnerabilityPublished 16 Mar 2026

CVE-2026-4203: D-Link DNS-120 · Command Injection

Affects D-Link DNS-120Source CVE Database V5

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Public exploit available · CVSS 5.3 Medium.

Data as of 29 Oct 2026, 19:04 UTC

CVSS 4.0 base score

5.3Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 4.3% chance of exploitation in 30 days – higher than 91% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/E:P

Base metrics

Attack Vector: Network
Attack Complexity: Low
Attack Requirements: None
Privileges Required: Low
User Interaction: None
Vulnerable system confidentiality: Low
Vulnerable system integrity: Low
Vulnerable system availability: Low
Subsequent system confidentiality: None
Subsequent system integrity: None
Subsequent system availability: None

Threat metrics

Exploit Maturity: POC

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, up to and including the entire Internet. Such a vulnerability is often termed “remotely exploitable” and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Attack Requirements: None: The successful attack does not depend on the deployment and execution conditions of the vulnerable system. The attacker can expect to be able to reach the vulnerability and execute the exploit under all or most instances of the vulnerability.
Privileges Required: Low: The attacker requires privileges that provide basic capabilities that are typically limited to settings and resources owned by a single low-privileged user. Alternatively, an attacker with Low privileges has the ability to access only non-sensitive resources.
User Interaction: None: The vulnerable system can be exploited without interaction from any human user, other than the attacker.
Vulnerable system confidentiality: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the Vulnerable System.
Vulnerable system integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact to the Vulnerable System.
Vulnerable system availability: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the Vulnerable System are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the Vulnerable System.
Subsequent system confidentiality: None: There is no loss of confidentiality within the Subsequent System or all confidentiality impact is constrained to the Vulnerable System.
Subsequent system integrity: None: There is no loss of integrity within the Subsequent System or all integrity impact is constrained to the Vulnerable System.
Subsequent system availability: None: There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System.
Exploit Maturity: POC: Based on threat intelligence sources each of the following must apply: · Proof-of-concept is publicly available · No knowledge of reported attempts to exploit this vulnerability · No knowledge of publicly available solutions used to simplify attempts to exploit the vulnerability

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 16 Mar 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: evidence found.
CVSS exploit maturity: proof of concept public
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), CVSS vector, the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
D-LinkDNS-120	Affected =20260205	Fixed in–
D-LinkDNR-202L	Affected =20260205	Fixed in–
D-LinkDNS-315L	Affected =20260205	Fixed in–
D-LinkDNS-320	Affected =20260205	Fixed in–
D-LinkDNS-320L	Affected =20260205	Fixed in–
D-LinkDNS-320LW	Affected =20260205	Fixed in–

AI-suggested

To mitigate CVE-2026-4203, organizations should immediately verify if their D-Link NAS devices are among the affected models and running vulnerable firmware versions (up to 20260205). The primary mitigation is to apply vendor-provided firmware updates or patches as soon as they become available. In the absence of patches, network-level mitigations should be implemented: restrict access to the device's management interfaces to trusted IP addresses only, preferably via VPN or internal network segments. Disable remote management features if not required. Employ network segmentation to isolate NAS devices from critical infrastructure and sensitive data environments. Monitor network traffic for unusual requests targeting the vulnerable CGI endpoints. Additionally, implement intrusion detection or prevention systems (IDS/IPS) with signatures for command injection attempts against these devices. Regularly audit device configurations and logs for signs of compromise. Educate users and administrators about the risks of exposing management interfaces to the internet. Finally, consider replacing outdated or unsupported devices with models that receive timely security updates.

Description

A vulnerability was detected 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. Impacted is the function cgi_portforwarding_add/cgi_portforwarding_del/cgi_portforwarding_modify/cgi_portforwarding_add_scan/cgi_dhcpd_lease/cgi_ddns/cgi_ip/cgi_dhcpd of the file /cgi-bin/network_mgr.cgi. The manipulation results in command injection. The attack may be launched remotely. The exploit is now public and may be used.

Impact

The impact of CVE-2026-4203 is significant for organizations relying on affected D-Link NAS devices. Successful exploitation can lead to remote command execution, allowing attackers to gain control over the device without authentication. This can result in unauthorized access to sensitive stored data, disruption of network services, and potential use of the compromised device as a foothold for further attacks within the internal network. Given the role of these devices in data storage and network management, attackers could manipulate network configurations, intercept or redirect traffic, or deploy malware. For enterprises, this could mean data breaches, operational downtime, and reputational damage. For home users or small businesses, the risk includes loss of personal or business data and potential inclusion in botnets or other malicious networks. The medium CVSS score reflects the balance between ease of exploitation and limited scope of impact, but the lack of authentication requirement and remote exploitability elevate the threat level. The public availability of exploit code increases the likelihood of opportunistic attacks, especially targeting unpatched devices.

Summary

CVE-2026-4203 is a command injection vulnerability identified in multiple D-Link NAS devices, including DNS-120, DNS-320, DNS-323, DNS-340L, DNS-345, DNS-726-4, and others, up to firmware version 20260205. The vulnerability resides in the /cgi-bin/network_mgr.cgi script, which handles network management functions such as port forwarding (cgi_portforwarding_add, cgi_portforwarding_del, cgi_portforwarding_modify, cgi_portforwarding_add_scan), DHCP lease management (cgi_dhcpd_lease), dynamic DNS (cgi_ddns), and IP configuration (cgi_ip, cgi_dhcpd). Due to insufficient input validation or sanitization, an attacker can inject arbitrary OS commands through crafted HTTP requests targeting these CGI endpoints. The attack vector is remote and does not require authentication or user interaction, making exploitation feasible over the network. The CVSS 4.0 vector indicates low attack complexity, no privileges required, and no user interaction, but with limited confidentiality, integrity, and availability impact (partial). The vulnerability could allow attackers to execute arbitrary commands with the privileges of the web server process, potentially leading to full device compromise, unauthorized data access, or lateral movement within the network. Although no confirmed exploitation in the wild is reported, the public availability of exploit code increases the risk of attacks. The affected devices are commonly used in small to medium business and home environments for network-attached storage, making them attractive targets for attackers seeking to compromise network infrastructure or exfiltrate data.

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 16 Mar 2026, 02:05 UTC

Technical details

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