CVE-2024-37036: Schneider Electric SAGE RTU Auth Bypass

CVE-2024-37036 Overview

CVE-2024-37036 is a critical out-of-bounds write vulnerability (CWE-787) affecting Schneider Electric SAGE RTU firmware. This vulnerability allows remote attackers to bypass authentication by sending a malformed POST request when particular configuration parameters are set. The flaw poses significant risks to industrial control systems (ICS) and operational technology (OT) environments that rely on these Remote Terminal Units (RTUs) for critical infrastructure operations.

Critical Impact

Successful exploitation could allow unauthenticated remote attackers to bypass authentication mechanisms, potentially gaining unauthorized access to SAGE RTU devices used in critical infrastructure environments including utilities, energy, and industrial automation sectors.

Affected Products

• Schneider Electric SAGE RTU Firmware (versions prior to patched release)
• Schneider Electric SAGE 1410
• Schneider Electric SAGE 1430
• Schneider Electric SAGE 1450
• Schneider Electric SAGE 2400
• Schneider Electric SAGE 3030 Magnum
• Schneider Electric SAGE 4400

Discovery Timeline

• 2024-06-12 - CVE-2024-37036 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2024-37036

Vulnerability Analysis

This out-of-bounds write vulnerability exists within the web interface component of Schneider Electric SAGE RTU devices. The vulnerability is particularly dangerous because it can be exploited remotely without requiring any user interaction or prior authentication. The flaw manifests when the device processes specially crafted HTTP POST requests, where improper boundary checking allows data to be written beyond allocated memory regions.

The vulnerability requires specific configuration parameters to be set on the target device, which may limit the attack surface in some deployment scenarios. However, when these conditions are met, the impact is severe as the out-of-bounds write condition can be leveraged to bypass authentication controls entirely.

Root Cause

The root cause of CVE-2024-37036 lies in improper input validation and boundary checking within the firmware's HTTP request handling routines. When processing POST request data, the firmware fails to properly validate the size of incoming data against allocated buffer boundaries. This allows an attacker to craft a malformed POST request that triggers a write operation beyond the intended memory buffer, corrupting adjacent memory regions that may contain authentication state or control flow data.

Attack Vector

The attack vector for this vulnerability is network-based, requiring no authentication or user interaction. An attacker with network access to the SAGE RTU device's web interface can exploit this vulnerability by:

1. Identifying a target SAGE RTU device with the vulnerable configuration parameters enabled
2. Crafting a malformed HTTP POST request designed to trigger the out-of-bounds write condition
3. Sending the malicious request to the device's web interface
4. Leveraging the memory corruption to bypass authentication mechanisms
5. Gaining unauthorized access to the RTU's management interface and control functions

The vulnerability does not require any prior knowledge of credentials or authenticated sessions, making it particularly dangerous for internet-exposed or insufficiently segmented industrial devices.

Detection Methods for CVE-2024-37036

Indicators of Compromise

• Unusual or malformed HTTP POST requests targeting the SAGE RTU web interface
• Authentication bypass events or unauthorized administrative sessions on SAGE RTU devices
• Unexpected configuration changes or command executions on RTU devices
• Network traffic anomalies including oversized POST request payloads directed at RTU management ports

Detection Strategies

• Implement network intrusion detection rules to identify malformed HTTP POST requests targeting SAGE RTU devices
• Deploy application-layer inspection to detect oversized or anomalous POST request bodies
• Monitor authentication logs on SAGE RTU devices for bypass indicators or suspicious access patterns
• Utilize SentinelOne Singularity platform for endpoint and network detection capabilities targeting OT/ICS environments

Monitoring Recommendations

• Enable detailed logging on SAGE RTU web interfaces to capture all authentication events
• Implement network segmentation monitoring to detect unauthorized access attempts to OT network segments
• Deploy anomaly detection for HTTP traffic patterns targeting industrial control devices
• Regularly audit SAGE RTU configuration parameters to identify potentially vulnerable settings

How to Mitigate CVE-2024-37036

Immediate Actions Required

• Review and apply the firmware update referenced in Schneider Electric Security Notice SEVD-2024-163-05
• Isolate affected SAGE RTU devices from untrusted networks until patches can be applied
• Implement network segmentation to restrict access to RTU management interfaces
• Review and harden configuration parameters on affected devices per vendor guidance
• Enable enhanced logging and monitoring on all SAGE RTU devices

Patch Information

Schneider Electric has released security guidance and firmware updates to address CVE-2024-37036. Organizations should consult the Schneider Electric Security Notice SEVD-2024-163-05 for detailed patch information, affected version numbers, and update procedures specific to their SAGE RTU model variants.

Workarounds

• Implement strict network access controls limiting HTTP/HTTPS access to SAGE RTU devices to authorized management stations only
• Deploy web application firewalls or intrusion prevention systems capable of inspecting and blocking malformed HTTP POST requests
• Disable unnecessary web interface features on SAGE RTU devices if not required for operations
• Utilize VPN tunnels or other encrypted channels for all remote management access to RTU devices

# Example network access control configuration
# Restrict HTTP/HTTPS access to SAGE RTU management interfaces

# Firewall rule to allow management access only from authorized subnet
iptables -A INPUT -p tcp --dport 80 -s 10.10.10.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -s 10.10.10.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP
iptables -A INPUT -p tcp --dport 443 -j DROP