CrushFTP warned customers of an unauthenticated HTTP(S) port access vulnerability and urged them to patch their servers immediately.

As the company also explained in an email sent to customers on Friday (seen by BleepingComputer), the security flaw enables attackers to gain unauthenticated access to unpatched servers if they are exposed on the Internet over HTTP(S).

“Please take immediate action to patch ASAP. A vulnerability has been addressed today (March 21st, 2025). All CrushFTP v11 versions were affected. (No earlier versions are affected.) A CVE will be generated soon,” the company warned.

“The bottom line of this vulnerability is that an exposed HTTP(S) port could lead to unauthenticated access. The vulnerability is mitigated If you have the DMZ feature of CrushFTP in place.”

While the email says this vulnerability only affects CrushFTP v11 versions, an advisory issued on the same day says that both CrushFTP v10 and v11 are impacted, as cybersecurity company Rapid7 first noted.

As a workaround, those who can’t immediately update CrushFTP v11.3.1+ (which fixes the flaw) can enable the DMZ (demilitarized zone) perimeter network option to protect their CrushFTP instance until security updates can be deployed.

According to Shodan, over 3,400 CrushFTP instances have their web interface exposed online to attacks, although BleepingComputer couldn’t determine how many have already been patched.

​In April 2024, CrushFTP also released security updates to patch an actively exploited zero-day vulnerability (CVE-2024-4040) that allowed unauthenticated attackers to escape the user’s virtual file system (VFS) and download system files.

At the time, cybersecurity company CrowdStrike found evidence pointing to an intelligence-gathering campaign, likely politically motivated, with the attackers targeting CrushFTP servers at multiple U.S. organizations.

CISA added CVE-2024-4040 to its Known Exploited Vulnerabilities catalog, ordering U.S. federal agencies to secure vulnerable servers on their networks within a week.

In November 2023, CrushFTP customers were also warned to patch a critical remote code execution vulnerability (CVE-2023-43177) in the company’s enterprise suite after Converge security researchers who reported the flaw released a proof-of-concept exploit three months after the flaw was addressed.

File transfer products like CrushFTP are attractive targets for ransomware gangs, specifically Clop, which was linked to data theft attacks targeting zero-day vulnerabilities in MOVEit Transfer, GoAnywhere MFT, Accelion FTA, and Cleo software.