CVE-2026-2364: CODESYS Privilege Escalation Vulnerability

CVE-2026-2364 Overview

A Time-of-Check Time-of-Use (TOCTOU) vulnerability exists in the CODESYS Development System installer that allows a low-privileged local attacker to gain elevated privileges on the affected system. The vulnerability is triggered when a legitimate user confirms a self-update prompt or initiates an installation of the CODESYS Development System. During this window, an attacker can exploit the race condition to manipulate files or resources between the security check and their subsequent use, resulting in unauthorized privilege escalation.

Critical Impact

Local attackers with low privileges can exploit the installer's race condition to gain elevated system rights, potentially compromising the entire development environment and any connected industrial control systems.

Affected Products

• CODESYS Development System (versions affected during self-update or installation processes)
• Systems running CODESYS installer components

Discovery Timeline

• 2026-03-10 - CVE CVE-2026-2364 published to NVD
• 2026-03-11 - Last updated in NVD database

Technical Details for CVE-2026-2364

Vulnerability Analysis

This vulnerability is classified as CWE-367 (Time-of-Check Time-of-Use Race Condition), a classic race condition vulnerability that affects the CODESYS installer's security validation process. The flaw occurs in the temporal gap between when the installer verifies the integrity or permissions of a resource (time-of-check) and when it actually uses that resource (time-of-use).

During the installation or self-update process, the CODESYS installer performs security checks on files, directories, or other resources before proceeding with elevated operations. However, due to the race condition, a local attacker can manipulate these resources in the brief window between the check and the use, causing the installer to operate on attacker-controlled content with elevated privileges.

The attack requires local access and user interaction (a legitimate user must initiate the update or installation), but once these conditions are met, an attacker with only low-level privileges can escalate to higher privilege levels on the system.

Root Cause

The root cause is a TOCTOU race condition (CWE-367) in the CODESYS installer's security validation logic. The installer fails to atomically verify and use resources, creating an exploitable window where an attacker can substitute malicious content for legitimate files after they have been validated but before they are used in privileged operations.

This architectural weakness stems from the installer not implementing proper atomic operations or file locking mechanisms during the update/installation process. The lack of synchronization between the verification step and the execution step allows concurrent modification of resources.

Attack Vector

The attack requires local access to the target system and depends on user interaction to trigger the vulnerable code path. An attacker must:

1. Position themselves on the same local system as a legitimate user with CODESYS Development System installed
2. Prepare malicious payloads or symbolic links to substitute during the race window
3. Wait for or socially engineer a legitimate user to initiate a self-update or new installation
4. Exploit the race condition by rapidly modifying resources between the check and use operations
5. Gain elevated privileges when the installer processes the attacker-controlled content

The attack mechanism involves exploiting the race condition window during the CODESYS installer's file validation process. When a legitimate user initiates an update or installation, the installer checks file permissions and integrity before executing operations with elevated privileges. An attacker monitoring this process can substitute malicious content at the precise moment between validation and execution. This technique commonly involves symbolic link manipulation, directory junction attacks, or rapid file replacement to redirect privileged operations to attacker-controlled resources. For complete technical details, see the CERTVDE Security Advisory VDE-2026-012.

Detection Methods for CVE-2026-2364

Indicators of Compromise

• Unexpected symbolic links or directory junctions created in CODESYS installation directories
• Anomalous file modification timestamps on installer-related files during update operations
• Evidence of rapid file replacements or race condition exploitation attempts in file system audit logs
• Unusual process spawning patterns during CODESYS installer execution

Detection Strategies

• Monitor for suspicious file system activity during CODESYS installer operations, particularly rapid file modifications or symbolic link creation
• Implement file integrity monitoring on CODESYS installation directories and temporary folders used during updates
• Configure endpoint detection to alert on privilege escalation attempts coinciding with installer processes
• Enable detailed process auditing to capture parent-child process relationships during installation operations

Monitoring Recommendations

• Enable Windows Security Event logging for process creation (Event ID 4688) and privilege use events
• Deploy SentinelOne Singularity platform for real-time behavioral analysis of installer processes
• Monitor %TEMP% and CODESYS installation directories for file system anomalies
• Implement alerting for any new services or scheduled tasks created during installer execution windows

How to Mitigate CVE-2026-2364

Immediate Actions Required

• Review and apply updates from CODESYS as referenced in the CERTVDE Security Advisory VDE-2026-012
• Restrict local user access on systems running CODESYS Development System to only authorized administrators
• Ensure CODESYS updates are performed only in controlled environments with limited user access
• Monitor installation and update processes for any signs of exploitation attempts

Patch Information

Consult the CERTVDE Security Advisory VDE-2026-012 for official patch availability and update instructions from CODESYS. Apply vendor-provided patches as soon as they become available to address the TOCTOU vulnerability in the installer.

Workarounds

• Perform CODESYS installations and updates only from accounts with administrator privileges on isolated systems where low-privileged users do not have access
• Disable or restrict local user accounts on development workstations during installation or update procedures
• Implement application whitelisting to prevent unauthorized executables from running during installer operations
• Consider network isolation of development systems during update processes to reduce attack surface

Mitigating TOCTOU vulnerabilities requires operational controls since no code-based workaround is available for end users. Ensure installations occur in single-user environments by restricting interactive logon sessions during the update window. Consider implementing mandatory access controls through Windows Security Policy or third-party endpoint protection to limit which processes can modify files in CODESYS installation directories during update operations.