# Critical RCE Vulnerability in Contemporary Controls BASC 20T Allows Full Network Takeover


## The Threat


Contemporary Controls' BASC 20T building automation controller contains a critical vulnerability that allows unauthenticated attackers to remotely compromise affected systems without any user interaction. The flaw, tracked as CVE-2025-13926, stems from the product's reliance on untrusted network inputs to make security decisions, creating a dangerous attack surface for critical infrastructure environments.


An attacker with network access to an affected device can sniff traffic between legitimate users and the controller, extract information about the communication protocol, and forge malicious packets to impersonate legitimate requests. This network sniffing and packet forgery approach bypasses authentication entirely, giving attackers complete control over the device and any systems it manages.


Once compromised, an attacker gains the ability to enumerate all functionality and components associated with the programmable logic controller (PLC), reconfigure device settings, rename or delete critical files, perform unauthorized file transfers, and execute arbitrary remote procedure calls. For building automation systems controlling HVAC, electrical distribution, access control, and other critical infrastructure, this level of access represents a catastrophic security failure.


## Severity and Impact


| Aspect | Details |

|--------|---------|

| CVE ID | CVE-2025-13926 |

| CVSS v3.1 Score | 9.8 (CRITICAL) |

| Vector String | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |

| Attack Vector | Network |

| Attack Complexity | Low |

| Privileges Required | None |

| User Interaction | None |

| Scope | Unchanged |

| Confidentiality Impact | High |

| Integrity Impact | High |

| Availability Impact | High |

| CWE | CWE-807: Reliance on Untrusted Inputs in a Security Decision |


The CVSS 9.8 rating reflects the severity of a vulnerability that requires no authentication, no user interaction, and no elevated privileges to exploit. An attacker on the same network segment as the affected controller can launch an attack immediately. This is particularly dangerous in critical infrastructure environments where building automation systems often operate across multiple facilities and geographic locations.


## Affected Products


  • Contemporary Controls BASC 20T

    • - BASControl20 version 3.1


    Contemporary Controls has classified the BASC 20T as an obsolete product. While the affected product line may no longer be actively marketed, many organizations continue running legacy industrial control systems well past their intended end-of-life dates, making this vulnerability relevant for legacy infrastructure environments.


    ## Mitigations


    ### For Legacy System Operators


    Contemporary Controls recommends that organizations using the affected BASC 20T contact the vendor directly for additional support and guidance. Given the product's obsolete status, traditional vendor patching may not be available. Organizations should contact Contemporary Controls' technical support at https://www.ccontrols.com/support/contacttech.htm to discuss options, including potential firmware updates, replacement hardware, or transition plans to supported products.


    ### Defensive Measures


    CISA recommends organizations implement immediate network-level protections to minimize exposure:


  • Network Isolation: Ensure all building automation control systems are not directly accessible from the internet. Place these devices behind firewalls and segregate them from corporate business networks using air-gapped or heavily restricted network segments.

  • VPN and Remote Access: If remote access to control systems is absolutely necessary, implement virtual private networks (VPNs) as a protective layer. Maintain VPN infrastructure at the latest available version, as VPNs themselves can contain vulnerabilities. Remember that a VPN is only as secure as the devices connected to it.

  • Traffic Monitoring: Implement network monitoring and intrusion detection to identify suspicious communication patterns, including network sniffing attempts or forged packets targeting the affected devices.

  • Risk Assessment: Before implementing any defensive measures, conduct a thorough impact analysis and risk assessment specific to your environment. Document which systems depend on the BASC 20T and develop a detailed transition or hardening plan.

    • ### Long-Term Remediation


    Organizations should prioritize replacing obsolete BASC 20T hardware with current, supported building automation controllers that receive regular security updates. Develop a formal lifecycle management program for industrial control systems with clear timelines for retiring unsupported products.


    ## References


  • CISA Alert: https://www.cisa.gov (Search for CVE-2025-13926)
  • CVE Details: https://www.cve.org/CVERecord?id=CVE-2025-13926
  • CWE-807: https://cwe.mitre.org/data/definitions/807.html
  • Vendor Support: https://www.ccontrols.com/support/contacttech.htm
  • CISA ICS Guidance: https://www.cisa.gov/ics

    • ---


    No public exploits for this vulnerability have been reported to CISA at this time. However, the criticality of the flaw and the straightforward attack vector (network sniffing and packet forgery) mean that exploitation is technically feasible for moderately skilled attackers. Organizations with obsolete BASC 20T systems in operation should treat this as a high-priority remediation target.