VulnerabilityPublished 15 Mar 2026Updated 17 Mar 2026

CVE-2026-4166: Wavlink WL-NU516U1 · Cross-site Scripting

Affects Wavlink WL-NU516U1Source CVE Database V5

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Public exploit available · CVSS 5.1 Medium.

Data as of 30 Oct 2026, 11:52 UTC

CVSS 4.0 base score

5.1Medium

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

EPSS: 0.2% chance of exploitation in 30 days – higher than 10% 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:P/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:P

Base metrics

Attack Vector: Network
Attack Complexity: Low
Attack Requirements: None
Privileges Required: Low
User Interaction: Passive
Vulnerable system confidentiality: None
Vulnerable system integrity: Low
Vulnerable system availability: None
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: Passive: Successful exploitation of this vulnerability requires limited interaction by the targeted user with the vulnerable system and the attacker’s payload. These interactions would be considered involuntary and do not require that the user actively subvert protections built into the vulnerable system.
Vulnerable system confidentiality: None: There is no loss of confidentiality within 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: None: There is no impact to availability within 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 15 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
WavlinkWL-NU516U1	Affected =240425	Fixed in–

AI-suggested

To mitigate CVE-2026-4166, organizations should first check for any firmware updates or patches released by Wavlink addressing this vulnerability and apply them immediately. In the absence of an official patch, administrators should restrict access to the router’s web management interface by limiting it to trusted internal networks and disabling remote management if enabled. Implement network-level controls such as firewall rules to block unauthorized access to the router’s management ports (typically TCP 80/443). Educate users and administrators about the risks of clicking on unsolicited or suspicious links that could exploit this XSS vulnerability. Employ web browser security features such as disabling JavaScript on the router’s management domain or using browser extensions that block cross-site scripting attacks. Monitor network traffic and logs for unusual access patterns or repeated attempts to exploit the vulnerability. Consider segmenting network management interfaces away from general user networks to reduce exposure. Finally, maintain an incident response plan to quickly address any signs of compromise related to this vulnerability.

Description

A vulnerability was found in Wavlink WL-NU516U1 240425. The impacted element is the function sub_404F68 of the file /cgi-bin/login.cgi. The manipulation of the argument homepage/hostname results in cross site scripting. The attack can be launched remotely. The exploit has been made public and could be used. The vendor was contacted early about this disclosure.

Impact

The primary impact of CVE-2026-4166 is the potential for attackers to execute arbitrary JavaScript code in the context of the router’s web management interface. This can lead to session hijacking, theft of authentication cookies, redirection to malicious sites, or phishing attacks targeting network administrators or users managing the device. While the vulnerability does not directly compromise the router’s firmware or network traffic, successful exploitation can undermine the integrity and confidentiality of the management session, potentially allowing further attacks or unauthorized configuration changes if combined with other vulnerabilities. Organizations relying on the Wavlink WL-NU516U1 for network connectivity may face increased risk of targeted attacks, especially in environments where users frequently access the router’s web interface. The requirement for user interaction limits automated exploitation but does not eliminate risk, particularly in phishing or social engineering scenarios. The absence of a patch increases exposure time, and public exploit availability may lead to increased scanning and exploitation attempts. Overall, the vulnerability poses a moderate risk to network security and operational integrity.

Summary

CVE-2026-4166 is a cross-site scripting vulnerability identified in the Wavlink WL-NU516U1 wireless router firmware version 240425. The issue resides in the CGI script /cgi-bin/login.cgi, specifically within the function sub_404F68, which processes the homepage/hostname parameter. Due to insufficient input validation and sanitization, an attacker can craft a malicious URL embedding JavaScript code in this parameter. When a user accesses this URL, the injected script executes within the context of the router's web management interface, potentially compromising the confidentiality and integrity of the user's session. The vulnerability is remotely exploitable without authentication, though it requires the victim to interact with the malicious link. The CVSS 4.0 base score is 5.1 (medium severity), reflecting the ease of remote exploitation but limited impact scope and the need for user interaction. No authentication or privileges are required, increasing the attack surface. Public exploit code is available, increasing the risk of opportunistic attacks targeting users of this router model. This vulnerability highlights the importance of robust input validation in embedded web interfaces of network devices.

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 23 Mar 2026, 00:32 UTC

Technical details

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