CVE-2024-11063: D-Link DSL6740C Firmware RCE Vulnerability

CVE-2024-11063 Overview

CVE-2024-11063 is an OS command injection vulnerability [CWE-78] affecting the D-Link DSL6740C modem. The flaw exists in a specific functionality exposed through the device's Secure Shell (SSH) and Telnet interfaces. Remote attackers holding administrator credentials can inject and execute arbitrary system commands on the underlying operating system. Successful exploitation grants full command execution in the device context, impacting confidentiality, integrity, and availability of the modem.

Critical Impact
Authenticated administrators can leverage SSH or Telnet to execute arbitrary OS commands on affected DSL6740C modems, enabling full device takeover, traffic interception, and pivoting into internal networks.

Affected Products

D-Link DSL6740C modem hardware
D-Link DSL6740C firmware (all versions listed in the TWCERT advisory)
Networks exposing SSH or Telnet management interfaces on the DSL6740C

Discovery Timeline

2024-11-11 - CVE-2024-11063 published to the National Vulnerability Database (NVD)
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2024-11063

Vulnerability Analysis

The DSL6740C exposes administrative functionality over SSH and Telnet. One or more command handlers accept user-controlled input that is passed to a shell interpreter without adequate sanitization. This behavior classifies as CWE-78: Improper Neutralization of Special Elements used in an OS Command.

An authenticated administrator can embed shell metacharacters such as ;, |, &&, or backticks within parameters processed by the vulnerable command. The device then executes the injected commands with the privileges of the invoking service, which on consumer modems typically runs as root.

Because the modem sits at the network perimeter, code execution provides a foothold for DNS hijacking, traffic capture, credential theft, and lateral movement into subscriber networks.

Root Cause

The root cause is missing input neutralization before OS command execution. The vulnerable functionality concatenates attacker-controlled parameters into a shell command string rather than passing them as isolated arguments to a safe execution API. No allowlist or metacharacter filter blocks shell operators from reaching the interpreter.

Attack Vector

Exploitation requires network access to the SSH or Telnet management service and valid administrator credentials. The attack does not require user interaction. Attackers who obtain credentials through phishing, credential reuse, default password abuse, or a separate authentication weakness can reach the vulnerable handler and inject shell payloads. The vulnerability manifests when injected metacharacters break out of the intended parameter context and are executed by the underlying shell. Refer to the TWCERT Security Advisory for the affected functionality details.

Detection Methods for CVE-2024-11063

Indicators of Compromise

Unexpected SSH or Telnet sessions to the modem management interface from external or unusual internal addresses
New or modified files in writable paths on the modem, or unexpected outbound connections initiated by the device
Configuration changes to DNS servers, routing tables, or firewall rules on the DSL6740C without an authorized change record
Administrator logins outside normal maintenance windows or from geolocations inconsistent with operator activity

Detection Strategies

Alert on any Telnet (tcp/23) traffic to modem management interfaces, since Telnet should be disabled by policy
Inspect SSH command channels for shell metacharacters (;, |, `, $() inside parameters that normally take alphanumeric values
Correlate administrator authentication events with subsequent outbound connections from the modem to identify command-and-control activity

Monitoring Recommendations

Forward device syslog, authentication logs, and NetFlow to a centralized analytics platform for behavioral baselining
Track administrator credential usage and flag repeated failed logins followed by a successful login on SSH or Telnet
Monitor for firmware version drift and unauthorized configuration exports from the DSL6740C fleet

How to Mitigate CVE-2024-11063

Immediate Actions Required

Restrict SSH and Telnet management access to trusted administrative networks using ACLs on the modem and upstream firewalls
Disable Telnet entirely and require SSH with strong, unique administrator credentials
Rotate all administrator passwords on DSL6740C devices and audit accounts for unused or shared credentials
Review recent administrative sessions and configuration changes for signs of exploitation

Patch Information

No fixed firmware version is listed in the NVD entry or the referenced advisories at the time of writing. Operators should consult the TWCERT Incident Report and the TWCERT Security Advisory for vendor guidance, and contact D-Link support to confirm patch availability for the DSL6740C. If the device is end-of-life or unpatched, plan for replacement with a supported model.

Workarounds

Block inbound tcp/22 (SSH) and tcp/23 (Telnet) from the WAN interface at the modem and upstream boundary
Place the modem management plane on a dedicated administrative VLAN unreachable from user subnets
Enforce multi-factor authentication on any jump host used to reach modem management interfaces
Segment the modem from internal corporate assets to limit blast radius if the device is compromised

bash

# Configuration example: restrict management access at an upstream firewall
# Deny inbound Telnet and SSH to the modem from untrusted networks
iptables -A FORWARD -p tcp --dport 23 -d <modem_ip> -j DROP
iptables -A FORWARD -p tcp --dport 22 -d <modem_ip> ! -s <admin_subnet> -j DROP