VulnerabilityPublished 16 Mar 2026

CVE-2026-4204: 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 30 Oct 2026, 11:52 UTC

CVSS 4.0 base score

5.3Medium

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

EPSS: 3.8% chance of exploitation in 30 days – higher than 90% 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 30 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

Immediately isolate affected D-Link NAS devices from untrusted networks to reduce exposure.
Monitor network traffic for suspicious requests targeting /cgi-bin/gui_mgr.cgi and the vulnerable functions, especially those manipulating the f_user parameter.
Implement network-level access controls such as firewall rules or VPN-only access to restrict management interface exposure.
Disable or restrict access to the vulnerable CGI functions if possible via device configuration or custom firmware modifications.
Regularly check for and apply official firmware updates or patches from D-Link addressing this vulnerability.
Employ intrusion detection/prevention systems (IDS/IPS) with signatures for known exploit attempts targeting this vulnerability.
Conduct thorough audits of NAS device logs for signs of compromise or unauthorized command execution.
Where feasible, replace outdated or unsupported devices with newer models that have improved security controls.
Educate IT staff about the vulnerability and ensure rapid incident response procedures are in place.
Consider network segmentation to limit the impact of a compromised NAS device on critical infrastructure.

Description

A flaw 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 affected element is the function cgi_myfavorite_add/cgi_myfavorite_set/cgi_myfavorite_del/cgi_myfavorite_set_sort_info/cgi_myfavorite_remove_apkg/cgi_myfavorite_compare_apkg/cgi_mycloud_auto_downlaod of the file /cgi-bin/gui_mgr.cgi. This manipulation of the argument f_user causes command injection. Remote exploitation of the attack is possible. The exploit has been published and may be used.

Impact

The impact of CVE-2026-4204 is substantial for organizations relying on affected D-Link NAS devices for data storage and network services. Successful exploitation allows remote attackers to execute arbitrary commands on the device, potentially leading to full device compromise. This can result in unauthorized access to sensitive data stored on the NAS, disruption or destruction of stored files, and the ability to use the compromised device as a foothold for lateral movement within internal networks. The integrity and availability of critical data and services hosted on these devices can be severely affected. Since the vulnerability requires no user interaction and can be exploited remotely, it increases the risk of automated attacks and worm-like propagation. Organizations without timely mitigation may face data breaches, operational downtime, and increased exposure to ransomware or other malware attacks. The lack of patches or official mitigation guidance further exacerbates the risk, making proactive defense essential.

Summary

CVE-2026-4204 is a command injection vulnerability identified in multiple D-Link NAS devices, including DNS-120, DNS-315L, DNS-320 series, DNS-323, DNS-340L, DNS-343, DNS-345, DNS-726-4, DNS-1100-4, DNS-1200-05, and DNS-1550-04, all up to firmware version 20260205. The vulnerability resides in the CGI script /cgi-bin/gui_mgr.cgi, specifically within several functions such as cgi_myfavorite_add, cgi_myfavorite_set, cgi_myfavorite_del, and others that handle the f_user parameter. Improper sanitization or validation of this parameter allows an attacker to inject arbitrary OS commands, which the device executes with the privileges of the web server process. This flaw can be exploited remotely over the network without requiring user interaction, although it requires low-level privileges (likely authenticated or with some access). The CVSS 4.0 vector indicates network attack vector, low attack complexity, no privileges required, no user interaction, and impacts on confidentiality, integrity, and availability, but with limited scope and impact severity. The exploit code has been publicly disclosed, increasing the likelihood of exploitation attempts. The vulnerability affects the core management interface of these devices, potentially allowing attackers to compromise device functionality, access stored data, disrupt services, or pivot into internal networks. No official patches or mitigation links are provided in the data, suggesting that affected organizations must seek vendor updates or apply workarounds. Given the widespread use of these D-Link NAS devices in small to medium enterprises and home environments, the vulnerability poses a significant risk if left unaddressed.

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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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