CVE-2021-42979 in Cloud Server
Summary
by MITRE • 12/07/2021
NoMachine Cloud Server is affected by Integer Overflow. IOCTL Handler 0x22001B in the NoMachine Cloud Server above 4.0.346 and below 7.7.4 allow local attackers to execute arbitrary code in kernel mode or cause a denial of service (memory corruption and OS crash) via specially crafted I/O Request Packet.
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Analysis
by VulDB Data Team • 12/10/2021
The vulnerability identified as CVE-2021-42979 represents a critical integer overflow flaw within the NoMachine Cloud Server kernel driver component. This vulnerability specifically affects versions of the software above 4.0.346 and below 7.7.4, creating a significant security risk for systems utilizing this remote desktop solution. The flaw exists within the IOCTL handler designated as 0x22001B, which processes input/output requests from user-space applications. The integer overflow condition occurs when processing specially crafted I/O Request Packets, potentially allowing attackers to manipulate the driver's memory handling mechanisms. From a cybersecurity perspective, this vulnerability aligns with CWE-190, which catalogs integer overflow and underflow conditions, and represents a classic example of a buffer manipulation attack vector that can lead to privilege escalation.
The technical exploitation of this vulnerability enables local attackers to achieve kernel-mode execution privileges, fundamentally compromising system integrity and security boundaries. When an attacker crafts malicious I/O Request Packets that trigger the integer overflow, the system's memory management becomes corrupted, leading to unpredictable behavior that can manifest as arbitrary code execution or system crashes. The operational impact extends beyond simple denial of service, as successful exploitation can result in complete system compromise, allowing attackers to execute malicious code with the highest system privileges. This vulnerability directly violates the principle of least privilege and creates a pathway for attackers to bypass standard security controls. The attack surface is particularly concerning given that NoMachine Cloud Server is commonly deployed in enterprise environments where remote access capabilities are essential but must maintain strict security boundaries.
The implications of this vulnerability extend to multiple cybersecurity frameworks and threat modeling approaches, including ATT&CK matrix techniques for privilege escalation and code execution. Attackers leveraging this vulnerability can potentially establish persistent access to systems, escalate privileges from standard user accounts to kernel-level access, and subsequently compromise entire network infrastructures. The vulnerability's classification as a local privilege escalation issue means that even if an attacker initially gains access through a different vector, they can use this flaw to elevate their privileges and gain complete control over affected systems. Organizations implementing NoMachine Cloud Server solutions must consider this vulnerability as part of their comprehensive security posture assessment, particularly in environments where physical access or local account compromise is possible. The memory corruption aspects of this vulnerability also make it particularly dangerous for systems running critical applications or those handling sensitive data, as the resulting system instability can lead to data loss or unauthorized data access.
Mitigation strategies for CVE-2021-42979 should prioritize immediate patching of affected NoMachine Cloud Server versions to ensure compliance with the vendor's security updates. Organizations should implement network segmentation and access controls to limit local system access where possible, reducing the attack surface for local privilege escalation attempts. Security monitoring should include detection of unusual I/O request patterns and kernel-level activity that might indicate exploitation attempts. System administrators should conduct thorough vulnerability assessments to identify all instances of affected software versions and ensure proper patch management processes are in place. Additionally, implementing behavioral monitoring solutions that can detect anomalous kernel activity or memory corruption patterns can provide early warning capabilities. The vulnerability also underscores the importance of maintaining up-to-date security practices, including regular security audits, proper access controls, and robust incident response procedures to address potential exploitation attempts. Organizations should also consider implementing automated patch management solutions to ensure rapid deployment of security updates across all affected systems.