CVE-2023-6340 in Capture Client
Summary
by MITRE • 01/18/2024
SonicWall Capture Client version 3.7.10, NetExtender client version 10.2.337 and earlier versions are installed with sfpmonitor.sys driver. The driver has been found to be vulnerable to Denial-of-Service (DoS) caused by Stack-based Buffer Overflow vulnerability.
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Analysis
by VulDB Data Team • 06/11/2025
The SonicWall Capture Client and NetExtender client software represents critical network security infrastructure components that facilitate secure remote access and network monitoring capabilities for enterprise environments. These applications are widely deployed across corporate networks to establish encrypted connections between remote users and internal resources, making them attractive targets for cyber adversaries seeking to disrupt business operations. The vulnerable sfpmonitor.sys driver component serves as a kernel-mode module responsible for system monitoring functions, particularly in relation to network interface monitoring and packet capture operations. This driver architecture places it at the core of system security operations where any vulnerability can potentially compromise the entire system integrity and availability.
The technical flaw manifests as a stack-based buffer overflow vulnerability within the sfpmonitor.sys driver, which occurs when the driver processes untrusted input data without proper bounds checking mechanisms. This vulnerability arises from insufficient validation of input parameters passed to kernel-mode functions, allowing malicious actors to craft specially crafted payloads that exceed the allocated stack buffer space. When the driver attempts to copy this oversized data into the fixed-size stack buffer, it overwrites adjacent memory locations including return addresses, function pointers, and other critical control data structures. The vulnerability is particularly concerning because it operates at kernel level where privilege escalation is not required for exploitation, meaning that an attacker can trigger the overflow from user-mode applications.
The operational impact of this denial-of-service vulnerability extends beyond simple system unavailability, as it can be leveraged to cause complete system crashes, reboot cycles, and potentially provide a foothold for further exploitation attempts. Network administrators may experience significant service disruption when affected systems become unresponsive, leading to productivity losses and potential data access interruptions. The vulnerability affects multiple versions of the software, including SonicWall Capture Client version 3.7.10 and NetExtender client versions 10.2.337 and earlier, indicating this represents a widespread issue affecting numerous enterprise deployments. The kernel-mode nature of the vulnerability means that successful exploitation can result in system instability that may persist until manual reboot occurs, creating extended downtime periods that can impact business continuity.
Security practitioners should prioritize immediate mitigation through vendor-provided patches and updates to address the underlying buffer overflow vulnerability in the sfpmonitor.sys driver. Organizations must implement network segmentation and monitoring to detect potential exploitation attempts targeting these vulnerable components. The vulnerability aligns with CWE-121 stack-based buffer overflow classification and represents a potential entry point for adversaries following ATT&CK technique T1489, which involves system denial of service through modification of system resources. Additionally, this vulnerability may facilitate subsequent attacks through privilege escalation or lateral movement if not properly addressed, making prompt remediation essential for maintaining overall network security posture. Regular security assessments and vulnerability scanning should include verification of driver versions and patch status to prevent exploitation of similar kernel-mode vulnerabilities in other network security components.