CVE-2026-47116: LTSecurity LTK3500SF Auth Bypass Vulnerability

CVE-2026-47116 Overview

CVE-2026-47116 is a hard-coded credentials vulnerability in the LTSecurity LTK3500SF device. The root and guest account passwords are stored in /etc/shadow as weak hashes that can be recovered with dictionary-based cracking tools. Once recovered, the credentials authenticate against the device's Telnet and SSH services and grant root-level access to the underlying operating system. Exploitation requires Telnet or SSH to be running, either by device configuration or manual start. The weakness is classified under CWE-798: Use of Hard-coded Credentials.

Critical Impact
An unauthenticated network attacker who cracks the embedded hashes gains persistent root-level shell access to the device, compromising confidentiality, integrity, and availability.

Affected Products

LTSecurity LTK3500SF (all firmware versions shipping the affected /etc/shadow hashes)
Telnet service on LTK3500SF when enabled or manually started
SSH service on LTK3500SF when enabled or manually started

Discovery Timeline

2026-09-22 - CVE-2026-47116 published to NVD
2026-09-23 - Last updated in NVD database

Technical Details for CVE-2026-47116

Vulnerability Analysis

The LTK3500SF ships with static, factory-provisioned passwords for the root and guest accounts. These credentials are embedded in the firmware image and land on the running device in /etc/shadow. Because the hashes rely on a weak algorithm and low-entropy passwords, an attacker with access to the firmware or filesystem can recover the plaintext values using standard dictionary attacks with tools such as hashcat or john.

The recovered plaintext is identical across every deployed device, so a single successful crack yields universal credentials. Any network-reachable LTK3500SF exposing Telnet or SSH accepts these credentials and returns a root shell. This turns a firmware-analysis problem into a network-wide compromise vector.

Root Cause

The root cause is the use of hard-coded credentials [CWE-798] combined with a weak password-hashing scheme in /etc/shadow. The manufacturer did not implement per-device unique credentials or forced first-boot password rotation. There is no mechanism to invalidate or rotate the embedded root and guest accounts through normal device configuration.

Attack Vector

The attack path proceeds in two stages. First, an attacker obtains the firmware image, either by downloading a vendor package or extracting flash contents from a device in their possession. They then run offline dictionary attacks against the root and guest hashes in /etc/shadow.

Second, the attacker scans networks for LTK3500SF devices exposing TCP/22 (SSH) or TCP/23 (Telnet). Where those services are running, the recovered credentials grant an interactive root shell. From that shell, the attacker can pivot into connected networks, alter device configuration, or install persistent implants. See the VulnCheck advisory for LTK3500SF and the proof-of-concept repository for technical details.

Detection Methods for CVE-2026-47116

Indicators of Compromise

Successful root or guest logins over SSH or Telnet on LTK3500SF devices from unexpected source IPs.
New or modified files in /root, /tmp, or /etc on the device following an inbound SSH or Telnet session.
Unexpected outbound connections initiated by the device to attacker-controlled infrastructure.
Telnet (TCP/23) or SSH (TCP/22) listeners active on LTK3500SF devices that should have management services disabled.

Detection Strategies

Inspect network flow data for inbound TCP/22 and TCP/23 sessions to LTK3500SF IP ranges, especially from external networks.
Correlate authentication events showing root or guest logins on LTK3500SF devices with baselines of authorized administrative activity.
Extract /etc/shadow from firmware images during procurement testing and confirm whether the shipped hashes match the publicly disclosed values.

Monitoring Recommendations

Forward device syslog and authentication logs to a centralized SIEM for continuous review of privileged logins.
Alert on any successful shell session on LTK3500SF devices outside change windows.
Monitor for port scans targeting TCP/22 and TCP/23 across segments containing LTSecurity equipment.

How to Mitigate CVE-2026-47116

Immediate Actions Required

Disable Telnet and SSH on LTK3500SF devices unless required for active administration.
Block inbound TCP/22 and TCP/23 to LTK3500SF devices at the network boundary and restrict access to a dedicated management VLAN.
Inventory all deployed LTK3500SF units and identify which have management services enabled.
Rotate any shared credentials on adjacent systems that may have been exposed through a compromised device.

Patch Information

No vendor patch is referenced in the NVD entry for CVE-2026-47116 at the time of publication. Consult the VulnCheck advisory for the latest vendor response and remediation status. Because the credentials are embedded in firmware, remediation requires a firmware update from LTSecurity that removes the hard-coded accounts or enforces first-boot password rotation.

Workarounds

Place LTK3500SF devices behind a firewall that denies all inbound traffic except from a hardened jump host.
Where the device configuration allows, disable the guest account and change the root password, then verify the change persists across reboots and factory resets.
Apply strict access control lists on upstream switches to restrict which hosts can reach the device management interface.
Treat any LTK3500SF that cannot be firewalled or reconfigured as end-of-life and remove it from the network.

bash

# Configuration example: block Telnet/SSH to LTK3500SF from all but a management host
iptables -A FORWARD -p tcp -d <LTK3500SF_IP> --dport 22 -s <MGMT_HOST_IP> -j ACCEPT
iptables -A FORWARD -p tcp -d <LTK3500SF_IP> --dport 23 -s <MGMT_HOST_IP> -j ACCEPT
iptables -A FORWARD -p tcp -d <LTK3500SF_IP> --dport 22 -j DROP
iptables -A FORWARD -p tcp -d <LTK3500SF_IP> --dport 23 -j DROP