CVE-2018-8335 in Windows
Summary
by MITRE
A denial of service vulnerability exists in the Microsoft Server Block Message (SMB) when an attacker sends specially crafted requests to the server, aka "Windows SMB Denial of Service Vulnerability." This affects Windows Server 2012 R2, Windows RT 8.1, Windows Server 2012, Windows Server 2016, Windows 8.1, Windows 10, Windows 10 Servers.
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Analysis
by VulDB Data Team • 05/08/2023
The CVE-2018-8335 vulnerability represents a critical denial of service flaw within Microsoft's Server Message Block protocol implementation that fundamentally undermines the availability of targeted systems. This vulnerability specifically manifests when the SMB server component processes malformed or specially crafted requests that trigger unexpected behavior in the protocol handler. The flaw exists at the core of Microsoft's file sharing and network communication infrastructure, affecting a broad spectrum of operating systems including Windows Server 2012 R2, Windows RT 8.1, Windows Server 2012, Windows Server 2016, Windows 8.1, and various Windows 10 variants. The vulnerability falls under the CWE-121 category of buffer overflow conditions, specifically manifesting as a heap-based buffer overflow that occurs during the processing of SMB requests. This classification indicates that the vulnerability stems from improper handling of memory allocation and data processing within the SMB server implementation, creating a predictable pattern of system instability.
The technical exploitation of this vulnerability involves sending carefully constructed SMB packets that cause the server to enter an infinite loop or crash state, effectively rendering the file sharing services unavailable to legitimate users. Attackers can leverage this flaw without requiring authentication credentials, making it particularly dangerous as it can be exploited remotely over the network. The impact extends beyond simple service disruption to encompass complete system unresponsiveness, as the SMB server component becomes unstable and may require manual restart or system reboot to restore normal operations. This vulnerability aligns with the ATT&CK technique T1499.004 which describes denial of service attacks targeting network services, and specifically demonstrates how attackers can leverage protocol implementation flaws to achieve system compromise. The exploitation process typically involves sending malformed SMB2_SESSION_SETUP requests that cause the server to process invalid data structures, leading to memory corruption and subsequent system instability.
The operational impact of CVE-2018-8335 presents significant business continuity risks for organizations relying on SMB-based file sharing services, as the vulnerability can be exploited by both malicious actors and automated scanning tools to disrupt critical operations. Network administrators face the challenge of identifying and mitigating this vulnerability across multiple server platforms while maintaining service availability during remediation efforts. The vulnerability's widespread impact across Microsoft's product ecosystem means that organizations must implement coordinated patch management strategies across their entire infrastructure, from legacy Windows Server 2012 deployments to newer Windows Server 2016 environments. Organizations with extensive file sharing operations, particularly those utilizing SMB for critical business processes, face potential revenue loss and operational disruption when systems become unavailable due to this vulnerability. The flaw's remote exploitability without authentication requirements makes it particularly attractive to threat actors seeking to disrupt services, as demonstrated by various exploit kits and automated scanning tools that have been developed to target this specific vulnerability.
Mitigation strategies for CVE-2018-8335 primarily focus on applying Microsoft security patches released in their August 2018 security updates, which address the underlying buffer overflow conditions in the SMB server implementation. Network segmentation and firewall rules can provide temporary protection by blocking SMB traffic on ports 139 and 445, though this approach may impact legitimate business operations that depend on file sharing services. Organizations should implement continuous monitoring solutions to detect anomalous SMB traffic patterns that may indicate exploitation attempts, while also establishing incident response procedures to quickly address any successful exploitation events. The vulnerability's classification as a critical issue by Microsoft underscores the importance of immediate patch deployment, particularly in environments where SMB services are exposed to untrusted networks. Security teams should also consider implementing SMBv1 protocol disablement where possible, as SMBv1 is inherently less secure and more susceptible to various attack vectors including this particular vulnerability. Additionally, organizations should conduct thorough vulnerability assessments to identify all systems running affected versions of Windows, ensuring comprehensive coverage of their infrastructure against potential exploitation of this denial of service flaw.