CVE-2007-0217 in Internet Explorer
Summary
by MITRE
The wininet.dll FTP client code in Microsoft Internet Explorer 5.01 and 6 might allow remote attackers to execute arbitrary code via an FTP server response of a specific length that causes a terminating null byte to be written outside of a buffer, which causes heap corruption.
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Analysis
by VulDB Data Team • 01/12/2025
The vulnerability identified as CVE-2007-0217 represents a critical heap corruption flaw within the wininet.dll component of Microsoft Internet Explorer versions 5.01 and 6. This issue stems from improper memory management during FTP protocol handling, specifically when processing responses from FTP servers that contain data of a particular length. The vulnerability operates through a buffer overflow condition that occurs when the FTP client processes server responses, causing a null byte to be written beyond the allocated buffer boundaries. This type of memory corruption vulnerability falls under the CWE-121 category of stack-based buffer overflow, though the specific implementation in this case affects heap memory structures. The flaw demonstrates characteristics consistent with the ATT&CK technique T1203 which involves exploitation of memory corruption vulnerabilities to execute arbitrary code.
The technical implementation of this vulnerability exploits the FTP client's handling of response data through the wininet.dll library, which is responsible for Internet protocol communications in Windows systems. When Internet Explorer processes FTP server responses, it allocates memory buffers to store the received data. However, when the response data reaches a specific length, the parsing logic fails to properly terminate the string, causing the null byte to overwrite adjacent memory locations in the heap. This heap corruption creates an exploitable condition where attackers can manipulate memory contents to redirect program execution flow. The vulnerability is particularly dangerous because it allows remote code execution without requiring user interaction beyond visiting a malicious website hosting the compromised FTP server.
The operational impact of CVE-2007-0217 extends beyond simple remote code execution to encompass broader system compromise capabilities. Attackers leveraging this vulnerability can potentially gain full system control, escalate privileges, and establish persistent access to affected systems. The vulnerability affects a wide range of Windows platforms including Windows 2000, Windows XP, and Windows Server 2003, making it particularly concerning for enterprise environments where these older systems may still be operational. The exploitation process typically involves crafting a malicious FTP response that triggers the buffer overflow condition, followed by executing shellcode that leverages the corrupted heap memory. This vulnerability was particularly prevalent in the early 2000s when Internet Explorer 5.01 and 6 were widely deployed across corporate networks.
Mitigation strategies for CVE-2007-0217 primarily focus on immediate patch deployment and system hardening measures. Microsoft released security updates that addressed the buffer overflow condition in wininet.dll through proper bounds checking and memory management improvements. Organizations should implement network segmentation to limit FTP access from untrusted sources and disable unnecessary FTP functionality in web browsers. Browser security configurations should be enhanced to restrict active content execution and implement strict security policies for handling external resources. The vulnerability demonstrates the importance of secure coding practices and proper input validation, aligning with industry standards that emphasize defensive programming techniques. Additionally, implementing intrusion detection systems and monitoring for unusual FTP traffic patterns can help identify potential exploitation attempts. Regular security assessments and vulnerability scanning should include checks for outdated browser versions and unpatched systems to prevent exploitation of this and similar historical vulnerabilities.