Carrier Block Load Vulnerability: Risks of DLL Hijacking on Windows Systems

Carrier Block Load Vulnerability Uncovered: Uncontrolled Search Paths and DLL Hijacking Risks​

In a recent security advisory, Carrier has disclosed a vulnerability in its Block Load HVAC load calculation program that could have significant implications for organizations using this tool—even if you’re reading this on a Windows-powered system. The vulnerability, documented as CVE-2024-10930, centers on an uncontrolled search path element issue that has the potential to allow attackers to perform DLL hijacking and execute arbitrary code with escalated privileges.

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Executive Summary​

Security researchers have flagged a critical issue in Carrier’s Block Load program:

• Rating & Risk:
• CVSS v4 Base Score: 7.1
• CVSS v3.1 Base Score: 7.8
• Attack Complexity: Low
• Vulnerability Class: Uncontrolled Search Path Element (CWE-427)
• Affected Versions: Block Load versions 4.00, and 4.10 to 4.16
• Potential Impact: Successful exploitation could lead to arbitrary code execution with escalated privileges on systems hosting the vulnerable application.

The advisory serves as a wake-up call, especially for IT administrators managing industrial applications on Windows systems, underscoring the need for vigilance in controlling software updates and network exposures.

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Technical Details​

Unpacking the Vulnerability​

The core of the issue is an uncontrolled search path element vulnerability. This risk arises when a program does not validate or constrain the locations from which dynamic libraries (DLLs) are loaded. Consequently, a malicious actor might exploit this gap to substitute legitimate libraries with compromised versions—potentially gaining elevated privileges on the affected system.

• Nature of the Vulnerability:
• DLL Hijacking: By injecting a malicious DLL into the search path, attackers can make the application load code that wasn’t intended by the developers.
• Privilege Escalation: Once the malicious DLL is executed, it could allow the attacker to bypass normal security restrictions and operate with higher-level permissions.

Detailed Vulnerability Metrics​

• CVE-2024-10930 clearly outlines the flaw, with two distinct CVSS evaluations:
• CVSS v3.1 Vector: AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
• This vector reiterates the risks associated within a confined (local) access scenario but with no privileges required to launch the attack.
• CVSS v4 Vector: AV:L/AC:L/AT/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
• The updated CVSS v4 parameters reflect slight adjustments while maintaining a high base severity score.

These measurements highlight that the window for attackers is wider than one might expect, especially in environments where legacy systems or suboptimal update practices persist.

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Impact on Windows and IT Infrastructure​

Even if Carrier’s Block Load is an HVAC load calculation program, many organizations deploy such tools on Windows environments. The implications for IT security are multifaceted:

• System Compromise Risks:
  Running vulnerable applications can be the first domino in a larger chain of exploitation. For IT professionals, a compromised HVAC control system can lead to operational disruptions, especially in facilities where building management systems are interlinked.
• Network Exposure:
  With many industrial control systems deployed on networks managed by Windows servers and workstations, an uncontrolled search path element can become a vector for lateral movement. Attackers may use this vulnerability as an entry point into broader networks if proper segmentation and defenses are not in place.
• Historical Context:
  DLL hijacking is not new, but its resurgence in embedded and specialized software highlights that even applications not traditionally seen as high-risk can harbor vulnerabilities. Windows administrators should note that controlling external library loads is a best practice that extends beyond consumer software to mission-critical industrial applications.

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Mitigation and Best Practices​

Carrier’s advisory includes clear directives for mitigating this vulnerability:

• Immediate Software Update:
• Upgrade to Block Load v4.2 or later.
  This is the most straightforward step to ensure that the vulnerability is patched.
• Network Exposure Controls:
• Minimize network exposure:
  Ensure that any control systems are not directly accessible from the internet.
• Segment critical networks:
  Isolate control system networks behind robust firewalls to prevent unauthorized access.
• Secure Remote Access:
• Use Virtual Private Networks (VPNs):
  When remote access is necessary, employ VPNs that are maintained with the latest updates to avoid vulnerabilities.
• Perform impact analysis:
  Before deploying remote access solutions, evaluate the risks and implement layered security measures.
• Adopt CISA Recommendations:
• Familiarize yourself with the guidelines presented by the Cybersecurity and Infrastructure Security Agency (CISA).
• Engage in regular audits of system configurations, especially those that handle dynamic libraries and external path elements.

By following these recommendations, IT professionals can significantly reduce the risk of exploitation. Organizations should also consider conducting periodic reviews of all third-party software, even those used in niche industrial contexts, to ensure they meet current cybersecurity standards.

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Broader Implications for Industrial and Commercial Facilities​

The discovery of the Block Load vulnerability serves as a reminder of the interconnected nature of modern IT infrastructures:

• Industrial Systems Security:
• The vulnerability predominantly impacts critical infrastructure sectors such as commercial facilities. In many cases, these systems are the backbone of operational success and safety in large organizations.
• Legacy Software on Windows Platforms:
• Many industrial and building management systems run on Windows, often using older versions of software that may not have been designed with today’s cybersecurity challenges in mind.
• Defense-In-Depth Approach:
• Relying solely on software updates is not enough. Employing a layered defense strategy—combining updated software, robust network segmentation, and continuous monitoring—is imperative.

This incident should prompt administrators to re-assess their overall approach to software security, emphasizing proactive measures that preempt vulnerabilities before they can be exploited.

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Concluding Thoughts​

The Carrier Block Load vulnerability—marked by its relatively low attack complexity yet potentially severe impact—highlights the evolving nature of cybersecurity threats. For Windows administrators and IT professionals, the key takeaways are:

• Stay Proactive: Regularly update all software, especially control systems that may not seem immediately connected to everyday business operations.
• Maintain Vigilance on Legacy Systems: Even trusted software from established vendors like Carrier can harbor critical vulnerabilities.
• Adopt Layered Security Practices: Use network segmentation, controlled access, and modern defensive strategies to thwart potential attackers.

Security is a never-ending race against threats. Whether you’re managing an HVAC load calculation program or a Windows workstation, keeping your systems patched and your defenses robust is paramount. With the right measures in place, you can ensure that vulnerabilities such as the one in Carrier’s Block Load do not turn into full-blown security breaches.
Remember: In today’s fast-paced IT environment, staying informed and proactive is your best defense against cyber adversaries.

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Source: https://www.cisa.gov/news-events/ics-advisories/icsa-25-063-01