External risk intelligence

Modbus Protocol Authentication Bypass Vulnerability

CVE advisorySeverity: CRITICAL (CVSS 9.8)

CVE-2017-6034

An authentication bypass vulnerability exists in Schneider Electric Modicon Modbus protocol. Attackers can replay captured commands, potentially affecting industrial control systems and business continuity.

2Halo Surface Signal

Authentication Bypass

Schneider Electric Modbus Firmware

External exposure likelihood

Halo Surface Signal score for CVE-2017-6034

This vulnerability affects Modbus, an industrial protocol typically isolated within segmented operational technology networks. While the CVSS attack vector is network-based, these devices are rarely exposed directly to the public internet, making remote exploitation unlikely in standard secure deployment environments.

Horizon Alert

Summary of the vulnerability and why it matters

This vulnerability impacts Schneider Electric Modicon Modbus protocol, which transmits sensitive information without encryption. An attacker could replay captured commands to disrupt operations. This could affect industrial control systems by allowing unauthorized control actions.

Vulnerable Modbus protocol transmissions
Cleartext sensitive information replay
Unauthorized control of systems

Attack Path

How an attacker could exploit the issue

A replay attack can allow an attacker to control critical functions of affected industrial systems. The Modbus protocol transmits sensitive commands, such as run, stop, upload, and download, in cleartext. An attacker can capture these commands and replay them to manipulate the system. This could result in unauthorized operational changes, potentially impacting business continuity and safety.

Exposure condition: Modbus protocol used.
Attacker starting point: Network access.
Trigger and result: Replay commands for control.

Live Threat

Current exploitation, exposure, and threat context

This vulnerability could allow attackers to bypass authentication and replay sensitive commands, potentially disrupting operations. Sensitive information is transmitted without encryption, enabling attackers to capture and reuse commands like run, stop, upload, and download. The exploitation of this vulnerability poses a significant risk to business operations and data integrity.

Attacker skill level: Low.
Required access or conditions: Network access.
Business risk or urgency: High.

Priority actions

Operational Fix

Recommended remediation, mitigation, and detection steps

This vulnerability allows for an attacker to bypass authentication and replay sensitive commands. The Modbus protocol transmits sensitive information in cleartext, potentially enabling unauthorized control over affected systems. This presents a significant risk to operational integrity and data security.

Identify exposed Modbus assets.
Reduce exposure or isolate risk.
Apply vendor fix, verify, and monitor.

Frequently asked questions

What is the Schneider Electric Modicon Modbus protocol and what is it used for?

The Schneider Electric Modicon Modbus protocol is a communication system used in industrial environments. It allows different devices, often those involved in industrial control and automation, to exchange data and commands. This enables functions like monitoring and controlling machinery.

What kind of weakness does CVE-2017-6034 represent in Modbus?

CVE-2017-6034 is classified as an Authentication Bypass by Capture-Replay weakness. This means that an attacker can intercept legitimate commands sent over the Modbus protocol and then send those same commands back later to gain unauthorized control or access.

What is needed for an attacker to exploit this Modbus vulnerability?

An attacker needs network access to the Modbus protocol to exploit this vulnerability. The protocol transmits sensitive commands in cleartext, which means an attacker can capture these commands and replay them without needing any special authentication.

Who should be concerned about this Modbus vulnerability based on its exposure?

Organizations using the Modbus protocol should be concerned. While the vulnerability can be exploited over a network, it is unlikely to be directly accessible from the public internet in typical secure operational technology setups. However, any internal network access could pose a risk.

What is the first step to address the Modbus authentication bypass vulnerability?

The initial step for anyone running this technology is to identify any Modbus assets that might be accessible. Following that, efforts should focus on reducing or isolating any potential exposure of these assets and applying any fixes provided by the vendor.

References

Written by Nicholas Merritt

External-surface CVE analysis and Halo Surface Signal prioritization for Halo Threat Intelligence.