CVE-2020-18077 in FTPShell
Summary
by MITRE • 12/17/2021
A buffer overflow vulnerability in the Virtual Path Mapping component of FTPShell v6.83 allows attackers to cause a denial of service (DoS).
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Analysis
by VulDB Data Team • 12/24/2021
The vulnerability identified as CVE-2020-18077 represents a critical buffer overflow flaw within the Virtual Path Mapping functionality of FTPShell version 6.83. This issue resides in the software's handling of user-supplied input during path resolution operations, creating a potential entry point for malicious actors to disrupt service availability. The vulnerability specifically affects the FTPShell application's ability to process virtual path mappings, which are commonly used in file transfer protocols to create logical directory structures that may differ from physical filesystem layouts. The buffer overflow occurs when the application fails to properly validate the length of input data before copying it into fixed-size memory buffers, allowing attackers to overwrite adjacent memory regions with malicious data.
From a technical perspective, this vulnerability manifests as a classic stack-based buffer overflow within the Virtual Path Mapping component, where insufficient bounds checking permits data to exceed allocated buffer boundaries. The flaw enables attackers to craft specially formatted path mappings that trigger memory corruption during processing, potentially leading to application crashes or unexpected behavior. According to CWE classification, this vulnerability maps to CWE-121 Stack-based Buffer Overflow, which is characterized by insufficient validation of input data length relative to buffer capacity. The vulnerability's impact is categorized as a denial of service condition, as successful exploitation can cause the FTPShell application to terminate unexpectedly or become unresponsive, effectively denying legitimate users access to the file transfer services. The attack vector requires remote exploitation through the FTPShell interface, where an attacker can submit malicious path mapping requests that trigger the vulnerable code path.
The operational impact of CVE-2020-18077 extends beyond simple service disruption, as it can affect organizations relying on FTPShell for critical file transfer operations. When exploited, the vulnerability can lead to complete service outages, requiring system administrators to restart the application manually and potentially resulting in data transfer delays or failures. The vulnerability affects all systems running FTPShell v6.83, regardless of operating system platform, making it particularly concerning for enterprise environments where multiple users may be simultaneously accessing file transfer services. Organizations utilizing FTPShell for automated file transfers or integration with other systems face increased risk of operational disruptions, as the DoS condition can cascade through dependent applications and services. From an attacker's perspective, this vulnerability aligns with ATT&CK technique T1499.004 for Network Denial of Service, as it enables the exploitation of network-based services to render them unavailable to legitimate users.
Mitigation strategies for CVE-2020-18077 should prioritize immediate software updates from the vendor, as FTPShell v6.84 and subsequent releases contain patches addressing this specific buffer overflow condition. System administrators should implement network segmentation to limit access to FTPShell services and deploy intrusion detection systems to monitor for suspicious path mapping requests. Additionally, input validation should be strengthened at the application level to prevent malformed data from reaching vulnerable code paths, and regular security assessments should be conducted to identify similar vulnerabilities in other components. Organizations should also consider implementing automated patch management processes to ensure timely deployment of security updates across all systems. The vulnerability demonstrates the importance of proper memory management practices and input validation in preventing exploitation of buffer overflow conditions, aligning with security best practices outlined in various industry standards including ISO 27001 and NIST cybersecurity frameworks.