CVE-2010-20049 in LeapFTP
Summary
by MITRE • 08/20/2025
LeapFTP < 3.1.x contains a stack-based buffer overflow vulnerability in its FTP client parser. When the client receives a directory listing containing a filename longer than 528 bytes, the application fails to properly bound-check the input and overwrites the Structured Exception Handler (SEH) chain. This allows an attacker operating a malicious FTP server to execute arbitrary code on the victim’s machine when the file is listed or downloaded.
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Analysis
by VulDB Data Team • 08/20/2025
The vulnerability identified as CVE-2010-20049 represents a critical stack-based buffer overflow flaw within LeapFTP client software versions prior to 3.1.x. This type of vulnerability falls under the common weakness enumeration CWE-121, which specifically addresses stack-based buffer overflow conditions where insufficient bounds checking allows attackers to overwrite adjacent memory locations including the structured exception handler chain. The vulnerability manifests when the FTP client processes directory listings from remote servers, creating a dangerous execution environment where malicious actors can manipulate the client's behavior through carefully crafted input.
The technical exploitation of this vulnerability occurs through a specific input validation failure in the FTP client's parser component. When LeapFTP encounters a directory listing containing filenames exceeding 528 bytes in length, the application's insufficient input boundary checking causes a buffer overflow condition. This overflow specifically targets the Structured Exception Handler chain which is crucial for exception management in windows applications. The overwrite of the SEH chain allows attackers to redirect program execution flow to malicious code locations, effectively enabling arbitrary code execution on victim machines. This particular threshold of 528 bytes represents a well-defined buffer size limit that when exceeded triggers the exploitable condition.
The operational impact of this vulnerability extends beyond simple code execution, as it represents a privilege escalation vector that can be leveraged by remote attackers without requiring authentication or complex preconditions. The attack scenario requires only that a victim connects to a malicious FTP server and either views or downloads files from a directory listing containing oversized filenames. This makes the vulnerability particularly dangerous in environments where users frequently connect to untrusted FTP servers or where automated directory browsing occurs. The vulnerability aligns with ATT&CK technique T1059.007 for command and scripting interpreter, as successful exploitation enables attackers to execute arbitrary commands with the privileges of the affected user.
Mitigation strategies for CVE-2010-20049 primarily focus on immediate software updates and defensive programming practices. The most effective solution involves upgrading to LeapFTP version 3.1 or later where proper bounds checking has been implemented to prevent the buffer overflow condition. Additionally, network administrators should consider implementing firewall rules that restrict FTP traffic to trusted servers only, and disable automatic directory listing features where possible. The vulnerability demonstrates the importance of input validation and proper memory management practices as outlined in secure coding guidelines, particularly emphasizing the need for bounds checking and exception handling mechanisms. Organizations should also implement network monitoring to detect unusual FTP traffic patterns that might indicate exploitation attempts. This vulnerability serves as a reminder of the critical importance of maintaining up-to-date software and the potential for remote code execution vulnerabilities in network client applications.