Use After Free in RMCAST Driver Enables Remote Code Execution

Executive Summary

CVE-2026-54995 is a use-after-free vulnerability in the Reliable Multicast Transport Driver (RMCAST). This type of vulnerability occurs when a program continues to use memory after it has been freed, which can lead to unexpected behavior or code execution.

In this case, an unauthorized attacker can exploit this flaw over a network to execute arbitrary code on a vulnerable system. The vulnerability does not require any privileges or user interaction to be exploited.

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Detection Guidance

The provided context does not include specific detection methods or commands for identifying the use-after-free vulnerability in the Reliable Multicast Transport Driver (RMCAST). Detection typically involves checking for vulnerable versions of the driver or monitoring network traffic for anomalous multicast activity, but no details are available in the given resources.

To detect this vulnerability, you may need to refer to Microsoft's official guidance or security tools that scan for vulnerable components. However, no commands or tools are specified in the provided text.

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Impact Analysis

This vulnerability can have severe impacts if exploited:

• Remote Code Execution: An attacker can execute malicious code on your system without any prior access or interaction.
• Unauthorized Access: The attacker can gain control over the affected system, potentially accessing sensitive data or performing unauthorized actions.
• Network-Based Attack: Since the vulnerability is exploitable over a network, systems running the vulnerable RMCAST driver are at risk if exposed to untrusted networks.

The CVSS base score of 8.1 (Critical) indicates a high potential for damage, particularly in terms of confidentiality, integrity, and availability of the affected system.

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Compliance Impact

This vulnerability can impact compliance with several standards and regulations, depending on the context of the affected system:

• GDPR: If the vulnerable system processes personal data of EU citizens, a successful exploit could lead to unauthorized access or disclosure of this data. This may result in a breach of GDPR requirements for data protection and could trigger mandatory breach notifications and potential fines.
• HIPAA: For organizations handling protected health information (PHI), exploitation of this vulnerability could lead to unauthorized access to PHI, violating HIPAA's Security Rule. This could result in penalties and required corrective actions.
• Other Standards: Compliance frameworks like ISO 27001, NIST, or PCI DSS require organizations to maintain secure systems and protect against unauthorized access. Exploitation of this vulnerability could indicate a failure to meet these requirements, leading to compliance violations.

Organizations should assess their exposure to this vulnerability and take appropriate remediation steps to maintain compliance with applicable regulations.

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Mitigation Strategies

Based on the provided context, the following immediate steps are recommended to mitigate the vulnerability:

• Apply the latest security updates or patches provided by Microsoft for the Reliable Multicast Transport Driver (RMCAST). Refer to the Microsoft Security Response Center (MSRC) update guide for CVE-2026-54995.
• If a patch is not immediately available, consider disabling or restricting access to the RMCAST driver until a fix is applied.
• Monitor network traffic for unusual multicast activity that could indicate exploitation attempts.
• Review Microsoft's official documentation for additional workarounds or mitigations specific to this vulnerability.

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