CVE-2025-11786: Circutor SGE-PLC Buffer Overflow Flaw

CVE-2025-11786 Overview

CVE-2025-11786 is a high-severity stack-based buffer overflow vulnerability affecting Circutor SGE-PLC1000 and SGE-PLC50 programmable logic controllers running firmware version 9.0.2. The vulnerability exists in the SetUserPassword() function, where the newPassword parameter is directly embedded into a shell command string using sprintf() without any sanitization or validation. This unsanitized input is then executed via the system() function, enabling command injection attacks that execute arbitrary shell commands with the same privileges as the application.

This vulnerability is particularly concerning in industrial control system (ICS) environments where these PLCs are deployed for energy management and monitoring purposes. Successful exploitation could allow an attacker with adjacent network access to compromise the device, potentially affecting connected industrial systems.

Critical Impact

Attackers with low-privilege adjacent network access can inject arbitrary shell commands through the password change function, potentially gaining full control of industrial PLCs and impacting connected systems with CVSS 4.0 score of 8.5.

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-2025-11786 published to NVD
• 2025-12-03 - Last updated in NVD database

Technical Details for CVE-2025-11786

Vulnerability Analysis

This vulnerability is classified under CWE-121 (Stack-based Buffer Overflow), though the primary exploitation vector is command injection. The flaw resides in the SetUserPassword() function within the firmware. When a user attempts to change their password, the newPassword parameter is incorporated directly into a shell command string using the sprintf() function. The resulting string is then passed to the system() function for execution.

The CVSS 4.0 vector string CVSS:4.0/AV:A/AC:L/AT:N/PR:L/UI:N/VC:H/VI:L/VA:H/SC:H/SI:L/SA:H indicates that the attack requires adjacent network access (AV:A) with low attack complexity (AC:L) and low privileges (PR:L). No user interaction is required (UI:N), and successful exploitation results in high impact to confidentiality (VC:H), low impact to integrity (VI:L), and high impact to availability (VA:H). The subsequent system impacts are also significant with high confidentiality (SC:H) and availability (SA:H) impacts.

The EPSS score of 0.063% places this vulnerability in the 19.6th percentile, indicating a relatively low probability of exploitation in the wild at this time.

Root Cause

The root cause of this vulnerability is the lack of input validation and sanitization in the password change functionality. The SetUserPassword() function uses sprintf() to construct a shell command by directly concatenating user-supplied input without any filtering or escaping of special characters. This represents a fundamental secure coding failure where untrusted input is passed directly to command execution functions.

The absence of input sanitization allows shell metacharacters and command separators (such as ;, |, &&, or backticks) to be interpreted by the shell when the system() function executes the constructed command string.

Attack Vector

The attack vector requires adjacent network access, meaning the attacker must be on the same network segment as the vulnerable PLC device. With low-privilege authentication, an attacker can submit a malicious password value containing shell command injection payloads.

For example, an attacker could craft a newPassword value containing shell metacharacters that terminate the intended command and inject arbitrary commands. When the sprintf() function constructs the command string and system() executes it, the injected commands run with the application's privileges.

The vulnerability mechanism involves unsanitized user input being passed to sprintf() for command string construction, followed by execution via system(). Attackers can leverage shell metacharacters to break out of the intended command context and execute arbitrary commands. For detailed technical analysis, refer to the INCIBE-CERT security advisory referenced in the external references.

Detection Methods for CVE-2025-11786

Indicators of Compromise

• Unusual network traffic to/from PLCs on the local network segment
• Unexpected process execution or shell activity on PLC devices
• Authentication attempts with unusual or malformed password values containing shell metacharacters
• Anomalous system behavior or configuration changes on affected Circutor devices
• Unexpected outbound connections from PLC devices

Detection Strategies

Organizations should implement network-based detection to identify potential exploitation attempts:

1. Network Traffic Analysis: Monitor network traffic to Circutor PLC devices for unusual patterns, particularly HTTP/HTTPS requests to password change endpoints containing suspicious characters.

2. Intrusion Detection Systems: Configure IDS/IPS rules to detect command injection patterns in traffic destined for PLC management interfaces.

3. Log Analysis: Review authentication and system logs from affected devices for evidence of exploitation attempts or unauthorized command execution.

4. Behavioral Monitoring: Establish baselines for normal PLC behavior and alert on deviations that could indicate compromise.

Monitoring Recommendations

Deploy network segmentation monitoring to track access to industrial control system networks. Implement anomaly detection for PLC communication patterns. Enable comprehensive logging on network devices controlling access to ICS segments. Consider deploying dedicated ICS security monitoring solutions that understand OT protocols and can identify abnormal behavior in industrial environments.

SentinelOne Singularity platform provides endpoint detection and response capabilities that can identify post-exploitation activities, unusual process behavior, and command-and-control communications that may result from successful exploitation of this vulnerability.

How to Mitigate CVE-2025-11786

Immediate Actions Required

• Isolate affected Circutor SGE-PLC1000 and SGE-PLC50 devices from untrusted network segments
• Implement strict network access controls to limit which systems can communicate with PLCs
• Restrict access to PLC management interfaces to authorized personnel only
• Monitor authentication activity and system logs on affected devices
• Review and strengthen network segmentation between IT and OT environments

Patch Information

Organizations should consult the INCIBE-CERT advisory and contact Circutor directly for firmware updates that address this vulnerability. The advisory is available at: https://www.incibe.es/en/incibe-cert/notices/aviso-sci/multiple-vulnerabilities-circutor-products-0

Until patches are available and applied, organizations should implement compensating controls to reduce risk exposure.

Workarounds

In the absence of an official patch, implement network-level mitigations to reduce the attack surface:

Network segmentation is critical for protecting vulnerable industrial control systems. Ensure PLCs are isolated on dedicated network segments with strict access controls. Use firewalls to limit connectivity to only required management stations. Disable unnecessary network services on PLC devices where possible. Implement multi-factor authentication for accessing ICS network segments.

Consider implementing application-layer firewalls or proxies that can filter potentially malicious input before it reaches the vulnerable devices. Regular security assessments of ICS environments can help identify and address exposure to this and similar vulnerabilities.