Executive Summary
In April 2026, Schneider Electric disclosed a critical vulnerability (CVE-2024-3596) affecting all versions of its Modicon and Connexium managed network switches. This flaw resides in the RADIUS authentication protocol, where an attacker with a man-in-the-middle position can exploit the MD5-based Response Authenticator to forge authentication responses. Such exploitation could grant unauthorized access to protected network segments, leading to potential denial of service and compromise of confidentiality and integrity of connected devices.
This vulnerability underscores the persistent risks associated with legacy cryptographic protocols like MD5 in critical infrastructure. Organizations relying on RADIUS for network access control must reassess their configurations and consider transitioning to more secure authentication methods to mitigate such threats.
Why This Matters Now
The continued reliance on outdated cryptographic protocols in critical infrastructure poses significant security risks. Immediate action is required to update authentication mechanisms and protect against potential exploitation.
Attack Path Analysis
An attacker exploited the RADIUS protocol vulnerability (CVE-2024-3596) to intercept and modify authentication responses, leading to unauthorized access. They escalated privileges by altering Access-Reject responses to Access-Accept, granting higher-level access. The attacker moved laterally within the network by leveraging the compromised switch to access connected devices. They established command and control by maintaining persistent access through the manipulated authentication responses. Sensitive data was exfiltrated by rerouting network traffic through the compromised switch. The attack resulted in significant operational disruption and potential data breaches.
Kill Chain Progression
Initial Compromise
Description
The attacker exploited the RADIUS protocol vulnerability (CVE-2024-3596) to intercept and modify authentication responses, leading to unauthorized access.
Related CVEs
CVE-2024-3596
CVSS 9A vulnerability in the RADIUS protocol allows a local attacker to modify any valid response, potentially leading to denial of service and loss of confidentiality and integrity.
Affected Products:
Schneider Electric Connexium Managed Switches – All Versions
Schneider Electric Modicon Managed Switches – All Versions
Schneider Electric Modicon Redundancy Switches – All Versions
Exploit Status:
no public exploit
MITRE ATT&CK® Techniques
Adversary-in-the-Middle
ARP Cache Poisoning
DHCP Spoofing
Evil Twin
Proxy
Protocol Tunneling
Potential Compliance Exposure
Mapping incident impact across multiple compliance frameworks.
PCI DSS 4.0 – Ensure that security policies and operational procedures for managing firewalls are documented, in use, and known to all affected parties.
Control ID: 6.4.1
NYDFS 23 NYCRR 500 – Cybersecurity Policy
Control ID: 500.03
DORA – ICT Risk Management Framework
Control ID: Article 5
CISA ZTMM 2.0 – Network and Environment Segmentation
Control ID: Pillar 3
NIS2 Directive – Cybersecurity Risk Management Measures
Control ID: Article 21
Sector Implications
Industry-specific impact of the vulnerabilities, including operational, regulatory, and cloud security risks.
Utilities
Critical RADIUS vulnerability in Schneider Electric network switches threatens power grid infrastructure authentication systems, potentially enabling unauthorized access and operational disruption.
Oil/Energy/Solar/Greentech
Energy facilities using Modicon managed switches face authentication bypass risks that could compromise SCADA networks and enable malicious control of critical processes.
Food Production
Manufacturing plants rely on Schneider Electric switches for network segmentation; RADIUS vulnerabilities could allow lateral movement compromising production control systems and safety.
Water and Wastewater
Water treatment facilities using affected Connexium switches face authentication spoofing attacks that could disrupt network access controls and compromise operational technology security.
Sources
- Schneider Electric Modicon Network Managed Switcheshttps://www.cisa.gov/news-events/ics-advisories/icsa-26-160-01Verified
- SEVD-2026-104-02 Third-Party vulnerability on Modicon Networking Managed Switcheshttps://www.se.com/us/en/download/document/SEVD-2026-104-02/Verified
- NVD - CVE-2024-3596https://nvd.nist.gov/vuln/detail/CVE-2024-3596Verified
Frequently Asked Questions
Cloud Native Security Fabric Mitigations and ControlsCNSF
Aviatrix Zero Trust CNSF is pertinent to this incident as it would likely limit the attacker's ability to exploit the RADIUS protocol vulnerability, thereby reducing unauthorized access and subsequent lateral movement within the network.
Control: Cloud Native Security Fabric (CNSF)
Mitigation: The attacker's ability to exploit the RADIUS protocol vulnerability may have been constrained, reducing the likelihood of unauthorized access.
Control: Zero Trust Segmentation
Mitigation: The attacker's ability to escalate privileges would likely be constrained, reducing the scope of unauthorized access.
Control: East-West Traffic Security
Mitigation: The attacker's lateral movement within the network would likely be limited, reducing the reach to other devices.
Control: Multicloud Visibility & Control
Mitigation: The attacker's ability to maintain persistent control would likely be constrained, reducing ongoing unauthorized access.
Control: Egress Security & Policy Enforcement
Mitigation: The attacker's ability to exfiltrate sensitive data would likely be limited, reducing data loss.
The overall impact of the attack would likely be reduced, limiting operational disruption and data exposure.
Impact at a Glance
Affected Business Functions
- Industrial Control Systems
- Network Management
- Operational Technology
Estimated downtime: 3 days
Estimated loss: $50,000
Potential exposure of network configurations and connected device data.
Recommended Actions
Key Takeaways & Next Steps
- • Implement Encrypted Traffic (HPE) to secure data in transit and prevent interception.
- • Deploy Zero Trust Segmentation to enforce least privilege access and limit lateral movement.
- • Utilize East-West Traffic Security to monitor and control internal network communications.
- • Establish Egress Security & Policy Enforcement to detect and prevent unauthorized data exfiltration.
- • Enhance Threat Detection & Anomaly Response capabilities to identify and respond to suspicious activities promptly.
