CVE-2007-6181 in cygwin
Summary
by MITRE
Heap-based buffer overflow in cygwin1.dll in Cygwin 1.5.7 and earlier allows context-dependent attackers to execute arbitrary code via a filename with a certain length, as demonstrated by a remote authenticated user who uses the SCP protocol to send a file to the Cygwin machine, and thereby causes scp.exe on this machine to execute, and then overwrite heap memory with characters from the filename. NOTE: it is also reported that a related issue might exist in 1.5.7 through 1.5.19.
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Analysis
by VulDB Data Team • 07/29/2021
The vulnerability identified as CVE-2007-6181 represents a critical heap-based buffer overflow flaw within the cygwin1.dll library component of Cygwin versions 1.5.7 and earlier. This issue resides in the Windows compatibility layer that enables Unix-like applications to run on Windows systems through the Cygwin environment. The vulnerability specifically manifests when processing filenames with excessive lengths during file transfer operations, particularly through the Secure Copy protocol. The flaw allows attackers to manipulate heap memory allocation by crafting maliciously long filenames that exceed the buffer boundaries allocated by the vulnerable library. This type of vulnerability falls under CWE-121, which categorizes heap-based buffer overflow conditions where insufficient bounds checking permits writing beyond allocated memory regions.
The technical exploitation of this vulnerability occurs through a carefully crafted filename that triggers memory corruption during the file transfer process. When an authenticated remote user sends a file via SCP protocol to a vulnerable Cygwin system, the scp.exe utility processes the filename through the cygwin1.dll library. The library fails to properly validate or limit the length of the filename, allowing the attacker to overflow the heap buffer and overwrite adjacent memory locations. This memory corruption can be leveraged to overwrite critical program data structures, function pointers, or return addresses, ultimately enabling arbitrary code execution. The attack requires authentication to the system since SCP protocol access is needed to trigger the vulnerable code path, making this a context-dependent vulnerability that cannot be exploited remotely without proper credentials.
The operational impact of this vulnerability extends beyond simple code execution, as it represents a significant threat to system integrity and security within environments relying on Cygwin for Unix compatibility. Systems running vulnerable versions of Cygwin are susceptible to privilege escalation attacks, where attackers can gain unauthorized access to system resources and potentially compromise the entire host environment. The vulnerability affects not only individual file transfers but also broader network services that depend on the Cygwin libraries for secure file operations. Organizations using Cygwin for development, testing, or production environments face substantial risk since the flaw can be exploited to establish persistent backdoors or exfiltrate sensitive data through the compromised system. This vulnerability also demonstrates the importance of proper input validation in cross-platform compatibility layers and highlights the security implications of legacy software components that may not receive adequate security updates.
Mitigation strategies for CVE-2007-6181 require immediate patching of affected Cygwin installations to versions 1.5.20 or later, which contain the necessary fixes for the heap overflow condition. System administrators should implement network segmentation and access controls to limit SCP protocol usage to trusted networks and authenticated users only. Additionally, monitoring for unusual filename patterns or length variations in file transfer logs can help detect potential exploitation attempts. The vulnerability's classification under ATT&CK technique T1059.007 for command and scripting interpreter suggests that exploitation may involve command execution through the compromised system, making defensive measures such as application whitelisting and process monitoring essential. Organizations should also consider implementing intrusion detection systems that can identify patterns consistent with heap overflow exploitation attempts, particularly during file transfer operations. Regular security assessments and vulnerability scanning of Cygwin-dependent systems remain crucial for maintaining operational security and preventing exploitation of similar legacy vulnerabilities.