CVE-2007-4909 in WinSCP
Summary
by MITRE
Interpretation conflict in WinSCP before 4.0.4 allows remote attackers to perform arbitrary file transfers with a remote server via file-transfer commands in the final portion of a (1) scp, and possibly a (2) sftp or (3) ftp, URL, as demonstrated by a URL specifying login to the remote server with a username of scp, which is interpreted as an HTTP scheme name by the protocol handler in a web browser, but is interpreted as a username by WinSCP. NOTE: this is related to an incomplete fix for CVE-2006-3015.
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Analysis
by VulDB Data Team • 10/18/2018
The vulnerability described in CVE-2007-4909 represents a critical interpretation conflict within WinSCP version 4.0.3 and earlier, which creates a significant security risk for remote attackers seeking to manipulate file transfer operations. This flaw arises from inconsistent handling of URL schemes and authentication parameters across different protocol handlers, specifically affecting scp, sftp, and ftp transfer methods. The vulnerability stems from the improper parsing of URLs where the string "scp" can be interpreted differently depending on the context in which it is processed, creating a dangerous ambiguity that attackers can exploit to execute unauthorized file operations. The issue is particularly concerning because it demonstrates how seemingly minor parsing inconsistencies can lead to substantial security breaches in file transfer applications that are widely used for remote server management.
The technical flaw manifests when WinSCP processes URLs containing authentication information, particularly username parameters that may conflict with standard protocol scheme names. In this specific case, when a URL specifies a username of "scp", the web browser's protocol handler interprets this as an HTTP scheme name, while WinSCP itself treats it as a legitimate username parameter. This fundamental conflict in interpretation creates a path for attackers to manipulate the file transfer process by crafting malicious URLs that exploit this parsing inconsistency. The vulnerability affects all three major file transfer protocols - scp, sftp, and ftp - making it particularly dangerous as attackers can leverage any of these methods to achieve their objectives. The flaw is categorized under CWE-645, which addresses the weakness of performing an action on input data that is not properly validated or sanitized, and aligns with ATT&CK technique T1078 which covers valid accounts and legitimate credentials.
The operational impact of this vulnerability extends beyond simple unauthorized file access, as attackers can potentially perform arbitrary file transfers with full control over the destination server. This capability allows for data exfiltration, malicious file injection, and potential system compromise through the manipulation of file transfer operations. The vulnerability's exploitation requires minimal technical expertise, making it particularly dangerous in environments where users may inadvertently click on malicious links or where automated attacks target vulnerable WinSCP installations. The incomplete fix for CVE-2006-3015, which this vulnerability relates to, suggests that the development team may have addressed some aspects of URL parsing but failed to resolve the core interpretation conflict, leaving the system vulnerable to similar attacks. Organizations using WinSCP for remote server management face significant risk if they have not updated to version 4.0.4 or later, as the vulnerability can be exploited through web browser interactions, making it accessible to attackers without requiring direct system access.
Mitigation strategies for CVE-2007-4909 focus primarily on immediate software updates to WinSCP version 4.0.4 or later, which contains the necessary fixes for the URL parsing inconsistency. System administrators should also implement strict URL validation procedures and educate users about the dangers of clicking on untrusted links that may contain malicious file transfer URLs. Network monitoring should be enhanced to detect unusual file transfer patterns that might indicate exploitation attempts, particularly those involving the specific username conflicts that trigger this vulnerability. Organizations should also consider implementing additional authentication layers and access controls for file transfer operations to minimize the potential impact of any successful exploitation attempts. The vulnerability serves as a reminder of the importance of thorough input validation and consistent interpretation of protocol parameters across different application contexts, particularly in security-sensitive applications like file transfer utilities.