CVE-2026-7027: D-Link DSL-2740R Firmware XSS Vulnerability

CVE-2026-7027 Overview

A Cross-Site Scripting (XSS) vulnerability has been identified in the D-Link DSL-2740R router firmware version EU_01.15. The vulnerability exists within the Wireless Setup Section of the device's web administration interface, specifically in the handling of the "Wireless Network Name" argument. An attacker with administrative access can inject malicious scripts through this parameter, which may then be executed in the context of other users accessing the router's management interface.

Critical Impact
Authenticated attackers can inject malicious scripts via the Wireless Network Name field, potentially leading to session hijacking, credential theft, or unauthorized configuration changes on affected D-Link DSL-2740R routers.

Affected Products

D-Link DSL-2740R Firmware version EU_01.15
D-Link DSL-2740R Hardware

Discovery Timeline

2026-04-26 - CVE-2026-7027 published to NVD
2026-04-30 - Last updated in NVD database

Technical Details for CVE-2026-7027

Vulnerability Analysis

This vulnerability is classified as CWE-79 (Improper Neutralization of Input During Web Page Generation), commonly known as Cross-Site Scripting (XSS). The affected component resides in the Wireless Setup Section of the D-Link DSL-2740R's web-based administration interface. When an administrator configures the wireless network settings, the device fails to properly sanitize user-supplied input in the "Wireless Network Name" (SSID) field before rendering it back to the user interface.

The exploit requires high privileges (administrator access) and user interaction to trigger, which limits its immediate exploitability. However, once successfully exploited, an attacker can execute arbitrary JavaScript code within the security context of other administrative users who view the Wireless Setup page.

Root Cause

The root cause of this vulnerability is insufficient input validation and output encoding in the D-Link DSL-2740R firmware's web interface. The Wireless Setup Section does not properly sanitize special characters in the Wireless Network Name parameter before incorporating the value into the HTML response. This allows specially crafted input containing JavaScript or HTML elements to be stored and subsequently rendered in the browser of any user viewing the affected page.

Attack Vector

The attack is network-based and can be executed remotely against the router's web administration interface. An attacker with administrative credentials can navigate to the Wireless Setup Section and submit a malicious payload in the Wireless Network Name field. This stored XSS payload will then execute when any administrator subsequently accesses the Wireless Setup configuration page.

The attack scenario typically involves:

Attacker obtains administrative access to the router (through credential theft, default credentials, or other means)
Attacker injects malicious JavaScript code into the Wireless Network Name field
The payload is stored in the device configuration
When another administrator views the Wireless Setup page, the malicious script executes in their browser context

The exploit has been publicly disclosed and technical details are available through the VulDB vulnerability database.

Detection Methods for CVE-2026-7027

Indicators of Compromise

Unusual or suspicious strings containing JavaScript syntax (<script>, javascript:, onerror=, onload=) in the router's SSID configuration
Unexpected changes to the Wireless Network Name that include encoded characters or HTML entities
Browser console errors or unexpected script execution when accessing the router's Wireless Setup page

Detection Strategies

Review the current SSID configuration on D-Link DSL-2740R devices for suspicious content containing script tags or event handlers
Monitor network traffic for attempts to submit payloads containing XSS patterns to the router's administrative interface
Implement web application firewall rules to detect and block common XSS payload patterns in requests to router management interfaces

Monitoring Recommendations

Enable logging on network devices to track administrative access and configuration changes
Periodically audit wireless configuration settings for unexpected or malicious content
Monitor for authentication attempts and successful logins to the router's web interface from unexpected IP addresses

How to Mitigate CVE-2026-7027

Immediate Actions Required

Restrict administrative access to the D-Link DSL-2740R to trusted internal networks only
Change default administrative credentials and use strong, unique passwords
Consider implementing network segmentation to limit exposure of the router's management interface
Review current SSID configuration for any suspicious content and reset if necessary

Patch Information

As of the last update on 2026-04-30, no official patch information has been released by D-Link for this vulnerability. Users are advised to monitor the D-Link Security Resource page for security updates and firmware releases. Given that the D-Link DSL-2740R is an older model, users should verify whether the device is still within its supported lifecycle and consider upgrading to a more current device if no patch becomes available.

Additional technical details and threat intelligence can be found at the VulDB CTI entry.

Workarounds

Disable remote management features and only allow local administrative access
Implement access control lists (ACLs) to restrict which IP addresses can reach the router's web interface
Place the router's management interface behind a VPN or additional authentication layer
Consider replacing end-of-life devices with current models that receive regular security updates