CVE-2026-1596: D-Link DWR-M961 RCE Vulnerability

CVE-2026-1596 Overview

A command injection vulnerability has been discovered in D-Link DWR-M961 router firmware version 1.1.47. This vulnerability affects the function sub_419920 within the file /boafrm/formLtefotaUpgradeQuectel. An attacker can manipulate the fota_url argument to inject arbitrary commands, enabling remote code execution on the affected device.

Critical Impact

Remote attackers with low-level privileges can execute arbitrary system commands on affected D-Link DWR-M961 routers, potentially leading to complete device compromise, network infiltration, and persistent unauthorized access.

Affected Products

• D-Link DWR-M961 firmware version 1.1.47
• D-Link DWR-M961 devices with vulnerable FOTA upgrade functionality

Discovery Timeline

• 2026-01-29 - CVE-2026-1596 published to NVD
• 2026-01-29 - Last updated in NVD database

Technical Details for CVE-2026-1596

Vulnerability Analysis

This vulnerability is classified under CWE-74 (Improper Neutralization of Special Elements in Output Used by a Downstream Component), commonly known as injection. The flaw resides in the firmware's handling of over-the-air (FOTA) upgrade functionality, specifically within the Quectel modem update mechanism.

The vulnerable endpoint /boafrm/formLtefotaUpgradeQuectel processes user-supplied input through the fota_url parameter without proper sanitization. When the sub_419920 function processes this input, it fails to adequately validate or escape special characters, allowing an attacker to break out of the intended command context and inject malicious system commands.

The network-accessible nature of this vulnerability means that authenticated attackers can remotely target the device without requiring physical access. The exploit has been publicly disclosed, increasing the risk of active exploitation in the wild.

Root Cause

The root cause of this vulnerability is insufficient input validation and sanitization in the sub_419920 function. When the fota_url argument is processed for firmware update operations, the application directly incorporates user-controlled input into system commands without properly escaping shell metacharacters or validating the URL format. This design flaw enables command injection attacks where specially crafted input can execute arbitrary commands with the privileges of the web server process.

Attack Vector

The attack vector is network-based, requiring the attacker to have authenticated access to the router's web management interface. Once authenticated, an attacker can submit a malicious request to the /boafrm/formLtefotaUpgradeQuectel endpoint with a crafted fota_url parameter containing shell metacharacters and embedded commands. These injected commands are then executed on the underlying operating system, potentially allowing the attacker to gain persistent access, modify device configuration, intercept network traffic, or pivot to other devices on the network.

The vulnerability can be exploited by injecting command separators (such as ;, |, or $(...)) followed by arbitrary commands into the fota_url parameter. Due to the lack of proper input sanitization, these commands are passed directly to system execution functions. For detailed technical information, refer to the GitHub CVE Issue Discussion and VulDB CTI Report #343358.

Detection Methods for CVE-2026-1596

Indicators of Compromise

• Unexpected HTTP requests to /boafrm/formLtefotaUpgradeQuectel endpoint with unusual fota_url parameter values containing shell metacharacters
• Anomalous outbound network connections from the router to unknown external hosts
• Unexpected processes or services running on the device
• Modifications to device configuration files or firmware

Detection Strategies

• Monitor web server logs for requests to /boafrm/formLtefotaUpgradeQuectel containing suspicious characters such as ;, |, $(), or backticks in the fota_url parameter
• Implement network-based intrusion detection rules to identify command injection patterns targeting D-Link router management interfaces
• Deploy SentinelOne Singularity to detect post-exploitation behaviors and anomalous process execution on network segments containing vulnerable devices

Monitoring Recommendations

• Enable comprehensive logging on the D-Link DWR-M961 device and forward logs to a centralized SIEM for analysis
• Implement network traffic analysis to detect unusual command-and-control communications originating from router devices
• Schedule regular firmware integrity checks to identify unauthorized modifications

How to Mitigate CVE-2026-1596

Immediate Actions Required

• Restrict access to the router's web management interface to trusted networks only using firewall rules or access control lists
• Disable remote management functionality if not required for operations
• Implement strong authentication credentials and change default passwords immediately
• Segment the network to isolate potentially vulnerable IoT and networking devices

Patch Information

At the time of publication, users should check D-Link Security Resources for firmware updates addressing this vulnerability. Monitor vendor security advisories for patches to D-Link DWR-M961 firmware version 1.1.47 and later. Apply any available security updates as soon as they are released.

Workarounds

• Configure firewall rules to block external access to the router's management interface on ports 80 and 443
• If possible, disable the FOTA upgrade functionality through the device's configuration interface until a patch is available
• Implement a VPN solution for remote management instead of exposing the web interface directly

# Example iptables rules to restrict management access
# Block external access to router management ports
iptables -A INPUT -i eth0 -p tcp --dport 80 -j DROP
iptables -A INPUT -i eth0 -p tcp --dport 443 -j DROP
# Allow only trusted internal network
iptables -A INPUT -s 192.168.1.0/24 -p tcp --dport 80 -j ACCEPT
iptables -A INPUT -s 192.168.1.0/24 -p tcp --dport 443 -j ACCEPT