CVE-2018-20658 in Core FTP
Summary
by MITRE
The server in Core FTP 2.0 build 653 on 32-bit platforms allows remote attackers to cause a denial of service (daemon crash) via a crafted XRMD command.
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Analysis
by VulDB Data Team • 09/04/2025
The vulnerability identified as CVE-2018-20658 represents a critical denial of service flaw within Core FTP Server version 2.0 build 653 specifically affecting 32-bit platform deployments. This issue manifests through the improper handling of a crafted XRMD command, which is an extended remote deletion command used in ftp protocols. The vulnerability exists at the protocol level where the server fails to adequately validate input parameters before processing them, creating an exploitable condition that can be leveraged by remote attackers to disrupt service availability.
The technical implementation of this vulnerability stems from inadequate input validation mechanisms within the server's command processing logic. When the server receives a specially crafted XRMD command, it does not properly sanitize or validate the command parameters, leading to a condition where malformed data can trigger an unexpected termination of the ftp daemon process. This behavior aligns with CWE-121, which describes stack-based buffer overflow conditions that occur when insufficient bounds checking is performed on data structures. The flaw specifically affects the 32-bit architecture implementation, suggesting that the memory management and stack handling differences between 32-bit and 64-bit systems may contribute to the vulnerability's exploitation characteristics.
From an operational perspective, this vulnerability presents a significant risk to organizations relying on Core FTP Server for file transfer operations. Remote attackers can exploit this weakness without requiring authentication credentials, making it particularly dangerous as it can be executed from any network location. The impact extends beyond simple service disruption to potentially compromise business continuity and data availability, as the daemon crash would require manual intervention to restart the ftp service. The vulnerability's exploitability is enhanced by the fact that it requires minimal technical knowledge to execute, making it attractive to attackers seeking to disrupt services without sophisticated attack capabilities. This aligns with ATT&CK technique T1499.004 which covers network denial of service attacks that target application availability.
The mitigation strategies for this vulnerability should prioritize immediate patch application from the vendor, as this represents a known issue that has likely been addressed in subsequent releases. Organizations should also implement network segmentation and access controls to limit exposure of the ftp service to untrusted networks. Additionally, monitoring and logging of ftp command execution should be enhanced to detect potential exploitation attempts. Network-based intrusion detection systems can be configured to identify and block suspicious XRMD command patterns. The remediation approach should also include disabling unnecessary ftp commands and implementing proper input validation mechanisms at the application layer to prevent similar vulnerabilities from manifesting in other protocol implementations. Security teams should conduct comprehensive vulnerability assessments to identify other potential command injection or buffer overflow vulnerabilities within the ftp server implementation and related services.