Wing FTP Vulnerability Actively Exploited Globally

Menace actors are exploiting a critical-severity vulnerability in a server file switch answer to execute arbitrary code remotely with root and system privileges.

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First disclosed by researcher Julien Ahrens of RCE Safety on June 30, the flaw – tracked as CVE-2025-47812 – in Wing FTP Server, stems from improper dealing with of � – null bytes in Wing FTP’s net interface. In keeping with the CVE advisory, the vulnerability impacts variations earlier than 7.4.4 and carries a most CVSS rating of 10.0, underscoring its severity and ease of exploitation.

“This can be utilized to execute arbitrary system instructions with the privileges of the FTP service, root or system by default,” the CVE entry says.

Huntress noticed energetic exploitation of the flaw on July 1, simply in the future after the technical disclosure. Attackers used a crafted username with a null byte to bypass the authentication course of and inject malicious Lua code into server session recordsdata. These session recordsdata, as soon as processed throughout respectable web page hundreds equivalent to /dir.html, are robotically executed, leading to distant code execution.

The injected Lua payload usually takes the type of a downloader script utilizing system instructions equivalent to certutil to retrieve malware from exterior servers. In a single instance, the payload tried to obtain a beacon from an attacker-controlled server.

Microsoft Defender blocked the downloaded file, recognized as Trojan:Win32/Ceprolad.A and subsequently terminated the Wing FTP Server course of, disconnecting the attacker.

In keeping with Censys, 8,103 Wing FTP servers are uncovered to the web globally, of which 5,004 have accessible net interfaces. Nearly all of servers are hosted in america, China, Germany, the UK and India, making these nations probably the most affected by potential exploitation.

Safety researcher Ahrens stated the flaw originates from how Wing FTP’s authentication perform c_CheckUser parses usernames. By inserting a null byte within the username string, attackers trick the server into validating partial usernames. As a result of the unsanitized username is later written to session recordsdata as Lua code, this results in command injection when these recordsdata are learn.

After injecting Lua code into the session file, the code is executed with system or root privileges, relying on the working system, Ahrens stated. Wing FTP runs with elevated privileges by default and lacks sandboxing or privilege-dropping protections, amplifying the impact of the flaw.

Arctic Wolf warned that given the general public availability of proof-of-concept code and technical breakdowns, attackers will more likely to proceed concentrating on unpatched programs. The corporate confirmed that exploitation has included downloading malicious payloads, working reconnaissance instructions whoami, ipconfig and even making an attempt to put in distant administration instruments like ScreenConnect.

Wing FTP Server customers are urged to improve to model 7.4.4 instantly. Arctic Wolf emphasised that even when nameless login is disabled, any legitimate person credentials – together with weak passwords – may very well be used to set off the vulnerability.

Organizations ought to look at their session file directories and Wing FTP logs for suspicious entries and examine any anomalous person accounts equivalent to wing or wingftp which will have been created for persistence throughout exploitation makes an attempt.