CVE-2025-11789: Circutor SGE-PLC1000 Buffer Overflow Flaw

CVE-2025-11789 Overview

CVE-2025-11789 is a high-severity out-of-bounds read vulnerability affecting Circutor SGE-PLC1000 and SGE-PLC50 programmable logic controllers running firmware version 9.0.2. The vulnerability exists in the DownloadFile function, which improperly converts a user-supplied parameter to an integer using the atoi() function and subsequently uses this value as an index into the FilesDownload array without adequate bounds checking. An attacker providing an excessively large parameter value can force the system to access memory beyond the intended array boundaries, potentially exposing sensitive information from device memory.

This vulnerability is particularly concerning for industrial control system (ICS) and operational technology (OT) environments where Circutor PLCs are commonly deployed for energy management and power monitoring applications.

Critical Impact

Network-accessible out-of-bounds read vulnerability in industrial PLCs could expose sensitive configuration data, credentials, or operational parameters with a CVSS 4.0 score of 7.1 (HIGH). Low-privileged authenticated attackers can exploit this remotely without user interaction.

Affected Products

• Circutor SGE-PLC1000 Firmware version 9.0.2
• Circutor SGE-PLC1000 Hardware
• Circutor SGE-PLC50 Firmware version 9.0.2
• Circutor SGE-PLC50 Hardware

Discovery Timeline

• 2025-12-02 - CVE-2025-11789 published to NVD
• 2025-12-03 - Last updated in NVD database

Technical Details for CVE-2025-11789

Vulnerability Analysis

The vulnerability is classified as CWE-125 (Out-of-bounds Read), a memory corruption issue that occurs when software reads data past the end or before the beginning of the intended buffer. In the context of CVE-2025-11789, the DownloadFile function in Circutor's PLC firmware fails to validate the bounds of an integer parameter before using it as an array index.

The CVSS 4.0 vector (CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N) indicates:

• Attack Vector (AV:N): Network-accessible without physical access
• Attack Complexity (AC:L): Low complexity exploitation
• Privileges Required (PR:L): Low-level authentication needed
• Confidentiality Impact (VC:H): High confidentiality impact from information disclosure

The EPSS (Exploit Prediction Scoring System) probability is 0.034% with a percentile of 9.59, indicating relatively low predicted exploitation activity at this time.

Root Cause

The root cause stems from unsafe integer handling and missing bounds validation in the firmware's file download functionality. The atoi() function converts a string parameter to an integer without checking whether the resulting value falls within the valid index range of the FilesDownload array. The subsequent array access operation (&FilesDownload)[iVar2] directly uses this unchecked value as an index offset, allowing attackers to read arbitrary memory locations relative to the array's base address.

This represents a classic pattern of improper input validation combined with unsafe C language array indexing practices common in embedded firmware development.

Attack Vector

The attack vector is network-based, requiring only low-privilege authentication to the target PLC device. An attacker with network access to the device's management interface can craft malicious requests to the DownloadFile function with specially crafted parameter values.

The exploitation mechanism involves supplying an abnormally large integer value as the file index parameter. When this value exceeds the legitimate bounds of the FilesDownload array, the memory read operation extends beyond the array's allocated space, returning data from adjacent memory regions. This could include:

• Configuration parameters and device settings
• Network credentials or authentication tokens
• Operational data and historical readings
• Firmware code segments or internal state variables

Since the atoi() function will parse both positive and negative values, attackers may be able to read memory both before and after the array's location in memory, expanding the potential information disclosure surface.

Detection Methods for CVE-2025-11789

Indicators of Compromise

• Unusual or anomalous network requests to PLC web management interfaces with abnormally large numeric parameters
• Repeated DownloadFile API calls with out-of-range integer values in request parameters
• Memory access violations or unexpected behavior in PLC diagnostic logs
• Network traffic containing responses with unexpected data sizes from the file download endpoint

Detection Strategies

Organizations should implement the following detection strategies for CVE-2025-11789:

Network-Based Detection:

• Monitor HTTP/HTTPS traffic to Circutor PLC devices for requests containing the DownloadFile function with abnormally large parameter values
• Implement deep packet inspection rules to flag requests with integer parameters exceeding expected ranges
• Alert on repeated failed or anomalous file download attempts from single sources

Endpoint-Based Detection:

• SentinelOne Singularity™ platform provides behavioral analysis capabilities that can detect anomalous memory access patterns indicative of out-of-bounds read exploitation
• Deploy network sensors in ICS/OT environments to monitor PLC communication patterns
• Enable verbose logging on PLC devices where available to capture suspicious API activity

SIEM Integration:

• Create correlation rules for multiple file download attempts with sequential or large integer parameters
• Monitor for reconnaissance patterns targeting industrial control devices

Monitoring Recommendations

Implement continuous monitoring of network segments containing Circutor PLC devices. Establish baseline communication patterns for normal PLC operations and alert on deviations. Consider deploying industrial-specific intrusion detection systems (IDS) that understand ICS protocols and can identify malformed or malicious requests targeting embedded device APIs.

SentinelOne customers can leverage the platform's network visibility features to monitor traffic flows to and from vulnerable PLC devices, enabling rapid detection of exploitation attempts.

How to Mitigate CVE-2025-11789

Immediate Actions Required

• Identify all Circutor SGE-PLC1000 and SGE-PLC50 devices running firmware version 9.0.2 in your environment
• Implement network segmentation to isolate vulnerable PLCs from untrusted network segments
• Restrict network access to PLC management interfaces using firewall rules and access control lists
• Monitor the INCIBE-CERT advisory for firmware update availability
• Review and audit user accounts with access to affected PLC devices, removing unnecessary privileges

Patch Information

As of the last modification date (2025-12-03), organizations should consult the INCIBE-CERT security advisory for official remediation guidance from the Spanish National Cybersecurity Institute. Contact Circutor directly for firmware update availability and patch deployment instructions.

Organizations should prioritize patching based on device criticality and network exposure. Devices accessible from external networks or shared network segments should receive priority attention.

Workarounds

Until a firmware patch is available, implement the following compensating controls:

Network Isolation:
Place affected PLC devices on isolated network segments with strict ingress and egress filtering. Only allow necessary communication from trusted management hosts.

Access Control Hardening:
Review and restrict user accounts with access to the DownloadFile functionality. Implement the principle of least privilege for all PLC administrative access.

Virtual Patching:
Deploy web application firewall (WAF) rules or intrusion prevention system (IPS) signatures to block requests to the DownloadFile endpoint containing out-of-range integer parameters.

Enhanced Monitoring:
Increase logging verbosity and implement real-time alerting for any access to the vulnerable function endpoint until permanent remediation is applied.