CVE-2022-39220 is a Cross-site Scripting (XSS) vulnerability identified in the SFTPGo product, an SFTP server implemented in the Go programming language. Specifically, versions of SFTPGo prior to 2.3.5 contain an improper neutralization of input during web page generation in the SFTPGo WebClient interface. This vulnerability is classified under CWE-79, which involves the failure to properly sanitize or encode user-supplied input before including it in dynamically generated web pages. As a result, an attacker can inject malicious scripts into the web interface that other users or administrators might execute unknowingly. The exploitation of this vulnerability requires no authentication or user interaction beyond accessing the vulnerable web client interface, making it remotely exploitable by unauthenticated attackers. The malicious code injected could execute in the context of the victim's browser session, potentially leading to session hijacking, credential theft, or unauthorized actions within the web client. The vulnerability was publicly disclosed on September 20, 2022, and has been patched in version 2.3.5 of SFTPGo. No known workarounds exist, emphasizing the importance of timely patching. There are no known exploits in the wild reported to date. The vulnerability affects all versions of SFTPGo prior to 2.3.5, which are deployed wherever the product is used. Given that SFTPGo is a specialized SFTP server solution, the attack surface is primarily the web management interface exposed to administrators or users managing file transfers. The technical details indicate that the vulnerability arises from insufficient input validation or output encoding in the web client, a common vector for XSS attacks.

For European organizations using SFTPGo versions prior to 2.3.5, this vulnerability poses a moderate risk to the confidentiality and integrity of their file transfer management operations. Successful exploitation could allow attackers to execute arbitrary scripts in the context of the web client, potentially leading to theft of session cookies, unauthorized access to administrative functions, or manipulation of file transfer configurations. This could result in data leakage, unauthorized data modification, or disruption of secure file transfer workflows. While the vulnerability does not directly compromise the underlying SFTP protocol or server functionality, the web client is a critical management interface, and compromise here could facilitate broader attacks or lateral movement within the network. The lack of known exploits in the wild reduces immediate risk, but the absence of workarounds and the ease of exploitation mean that unpatched systems remain vulnerable. European organizations in sectors with high reliance on secure file transfer—such as finance, healthcare, government, and critical infrastructure—may face increased risk if they use vulnerable versions. Additionally, regulatory requirements such as GDPR impose strict data protection obligations, and exploitation leading to data breaches could result in significant legal and reputational consequences.

1. Immediate upgrade of all SFTPGo installations to version 2.3.5 or later to apply the official patch that addresses the XSS vulnerability. 2. Restrict access to the SFTPGo WebClient interface by implementing network segmentation and firewall rules to limit exposure only to trusted administrative networks or VPNs. 3. Employ Web Application Firewalls (WAFs) with custom rules to detect and block suspicious input patterns targeting the web client interface, providing an additional layer of defense. 4. Conduct regular security audits and penetration testing focusing on web interfaces of file transfer solutions to identify and remediate similar vulnerabilities proactively. 5. Educate administrators and users about the risks of XSS and encourage the use of strong, unique credentials and multi-factor authentication where supported to reduce the impact of session hijacking. 6. Monitor logs and network traffic for unusual activity around the SFTPGo web client, including unexpected script injections or anomalous access patterns. 7. If immediate patching is not feasible, consider temporarily disabling the web client interface or restricting it to read-only mode if supported, to minimize attack surface until the patch can be applied.