Carrier Block Load Vulnerability: Risks and Mitigations for IT and ICS

On February 20, 2025, the Cybersecurity and Infrastructure Security Agency (CISA) published an advisory outlining a critical vulnerability affecting Carrier's Block Load product—a specialized HVAC load calculation program widely used in commercial facilities. Though this advisory focuses on industrial control systems (ICS), its implications resonate well within the broader IT and Windows security communities, where interconnected networks demand a unified approach to vulnerability management.
In this article, we dive deep into the details of the vulnerability, its technical underpinnings, potential impact, and the recommended mitigations. We also reflect upon how industrial system weaknesses can serve as a proxy for broader network risk—especially in environments where Windows systems and ICS devices coexist.

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Overview of the Carrier Block Load Advisory​

Carrier’s Block Load product, specifically version 4.16, harbors an Uncontrolled Search Path Element vulnerability (CWE-427). This type of flaw allows an attacker to perform DLL hijacking—a technique that can enable the execution of arbitrary code with escalated privileges. Key points from the advisory include:

• CVSS Scores:
• CVSS v4: Base score of 7.1
• CVSS v3.1: Base score of 7.8
• Attack Characteristics:
• Exploitable remotely
• Low attack complexity
• Vulnerability Identifier: https://www.cve.org/CVERecord?id=CVE-2024-10930
• Research and Reporting:
• Discovered by an anonymous researcher who reported the vulnerability directly to Carrier
• Critical Sectors & Exposure:
• Primarily impacts commercial facilities across the United States

Given the potential for arbitrarily executing code with higher privileges, this flaw represents a significant security risk for organizations that rely on these specialized tools for HVAC load calculations.

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A Closer Look at the Technical Details​

Understanding CWE-427: Uncontrolled Search Path Element​

At its core, the vulnerability arises from an uncontrolled search path element in the Block Load application. When an application improperly validates or limits the directories it searches for executable files or DLLs, it becomes susceptible to DLL hijacking. In such scenarios, an attacker can plant a malicious DLL in a directory that the application searches—leading the application to load the rogue DLL instead of the legitimate one.
For IT and security professionals, this type of vulnerability is particularly concerning because:

• Attack Surface Expansion: Even if the software is not directly internet-facing, an attacker with network access can exploit the flaw remotely.
• Privilege Escalation: Once exploited, the vulnerability can facilitate arbitrary code execution with escalated privileges, meaning an attacker could potentially gain system-level access.
• Stealth and Ease: Given the low attack complexity, malicious actors may require only minimal interaction or misconfiguration to execute an attack successfully.

The Dual CVSS Assessment​

The advisory provides both a CVSS v3.1 and a CVSS v4 score:

• CVSS v3.1 (7.8):
• Vector String: AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
• This high score underscores the potential for serious impact once the vulnerability is exploited, despite the need for local access.
• CVSS v4 (7.1):
• Vector String: AV:L/AC:L/AT/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
• A slightly lower score in the newer vector reflects adjustments in scoring criteria while still indicating a significant threat level.

Understanding these scores helps inform risk assessments—especially in environments where industrial devices are networked alongside Windows systems, highlighting the necessity for consistent patching and layered security.

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Implications for Industrial and IT Environments​

Potential Impact on Affected Systems​

The direct consequence of the vulnerability is the possibility for an attacker to hijack the DLL search path and load a malicious library, leading to arbitrary code execution. In practical terms:

• Operational Disruption: In commercial facilities, the Block Load application plays a pivotal role in HVAC system management. An exploited vulnerability could, theoretically, disrupt operations or even manipulate system parameters.
• Credential and Data Risks: Attacks leading to privilege escalation can open the door to unauthorized data access and control. The integrity of the entire control system could be compromised.
• Propagation Risks: Once an industrial control system is compromised, attackers might pivot to other networked assets, including Windows-based systems. This lateral movement reinforces the need for comprehensive cross-system security.

Broader Security Concerns​

While this advisory specifically targets an ICS product, the ripple effects can extend beyond the immediate environment. Modern IT infrastructures are highly interconnected. For example, many organizations run a mix of Windows servers, desktops, and ICS devices on the same networks. This convergence means that:

• Network Segmentation is Vital: Ensuring that ICS devices are isolated from the broader business network can minimize risks.
• Timely Updates Matter Everywhere: Just as Microsoft emphasizes the importance of timely security patches for Windows 11 (among others), similar rigor is essential for ICS devices and specialized software.
• Shared Attack Vectors: Many vulnerabilities, whether on a Windows system or an industrial application, hinge on similar principles of misconfiguration or insufficient validation. A breach in one area may serve as the stepping stone for an attack in another.

In essence, while the Carrier Block Load vulnerability might seem niche, it is part of a larger trend towards exploiting every possible entry point into modern networks.

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Mitigation and Best Practices​

Immediate Steps for Affected Users​

Carrier recommends that all users upgrade the Block Load product to version 4.2 or later. Should any issues arise during the update process, users are encouraged to reach out directly to Carrier for support. The upgrade path mitigates the risk by eliminating the vulnerable search path condition.

Additional Mitigation Measures Recommended by CISA​

CISA further advises organizations to adopt broader defensive measures to minimize exploitation risks:

• Minimize Network Exposure:
• Avoid exposing control system devices directly to the internet.
• Implement strict firewall rules to reduce potential access vectors.
• Network Segmentation and Isolation:
• Separate ICS networks from business networks.
• Use dedicated subnets and VLANs to confine the impact of any breach.
• Secure Remote Access:
• If remote connections are required, use robust Virtual Private Networks (VPNs).
• Keep VPN software updated to mitigate known vulnerabilities, understanding that even secure remote access mechanisms can have their own issues.
• Rigorous Risk Assessments:
• Regularly perform vulnerability assessments on all connected systems, including those that one might assume are “out of sight.”
• Ensure that any changes or updates in one system do not inadvertently open new vulnerabilities in another.

Best Practices for Hybrid Environments​

For organizations that run Windows systems alongside ICS equipment, the following steps are particularly pertinent:

• Apply a Layered Security Approach:
• Use firewalls, intrusion detection systems (IDS), and endpoint security solutions to create multiple barriers against potential attackers.
• Regular Patch and Update Cycles:
• Stay current with updates for all systems, from Windows operating systems to niche applications like Carrier Block Load.
• Educate and Train Staff:
• Ensure IT teams are aware of both traditional IT threats and ICS-specific vulnerabilities.
• Regular security training can help teams recognize and react to emerging threats promptly.

Implementing these measures not only addresses the immediate risk posed by the Carrier vulnerability but also reinforces overall network security—a key concern for any organization managing a mix of Windows and industrial control systems.

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Broader Implications and Industry Reflections​

How ICS Vulnerabilities Affect the Wider Tech Landscape​

Industrial control systems were once thought to be isolated from traditional IT networks. However, with the convergence of operational technology (OT) and information technology (IT), vulnerabilities like the one in Carrier’s Block Load can no longer be ignored. They serve as stark reminders that:

• Interconnectivity Breeds Complexity: Modern networks, including those supporting Windows 11 updates or enterprise applications, often interact with legacy or specialized systems. A vulnerability in one area can have wide-reaching effects.
• The Importance of Proactive Security: Just as Microsoft has addressed issues ranging from end-of-support notifications for Windows 10 to the deprecation of outdated services like WSUS driver synchronization (as discussed in https://windowsforum.com/threads/352826), organizations must maintain a proactive stance on security. Each system, no matter how specialized, must be regularly evaluated and updated.
• A Call for Unified Cyber Defense Strategies: Cybersecurity is not limited to one sector. Best practices in ICS security—such as network isolation, robust VPN configurations, and regular vulnerability assessments—can and should be applied across all areas of an organization’s digital footprint.

Reflecting on Recent Industry Developments​

Discussions on Windows security updates, cloud integrations, and other evolving technologies are commonplace on our forum. For instance, our recent thread on "Disable Windows 10 End-of-Support Notifications: A User's Guide" (https://windowsforum.com/threads/352831) highlighted the practical challenges users face during transitions and upgrades. Vulnerabilities in specialized tools like Carrier Block Load only reinforce the broader narrative: staying ahead of security risks is an ongoing, multi-faceted effort.
The convergence of IT and OT means that whether you’re managing a fleet of Windows desktops or ensuring the accuracy of HVAC load calculations, cybersecurity best practices are paramount. This ongoing integration demands a holistic approach—one that does not compartmentalize security by system type but rather addresses the entire network ecosystem.

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Conclusion​

The Carrier Block Load vulnerability (CVE-2024-10930) is a critical reminder of the ever-present risks in today’s interconnected digital landscape. Even specialized applications used in industrial control systems are not immune to exploitation—underscoring the need for vigilant patching, risk assessment, and network segmentation. In light of this advisory, organizations using Carrier’s Block Load should prioritize an immediate upgrade to version 4.2 or later, while also implementing broader cybersecurity measures as recommended by CISA.
By understanding the technical details—such as the mechanics of DLL hijacking via uncontrolled search path elements—and coupling that with proactive mitigation strategies, IT and security professionals can better safeguard their environments. As our discussion here and in related threads (for example, https://windowsforum.com/threads/352826) shows, a unified and proactive approach remains the best defense against today's multifaceted cybersecurity challenges.
Staying informed, updating systems promptly, and isolating vulnerable components are key steps on the road to robust cybersecurity—whether you're managing industrial control systems or your Windows workstations.
Stay safe and keep your networks secure!

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Source: CISA https://www.cisa.gov/news-events/ics-advisories/icsa-25-051-03