CVE-2025-54309: CrushFTP Unprotected Alternate Channel Vulnerability

What it is

CrushFTP 10 before 10.8.5 and 11 before 11.3.4_23, when the DMZ proxy feature is not used, mishandles AS2 validation and consequently allows remote attackers to obtain admin access via HTTPS, as exploited in the wild in July 2025.

Exploitation evidence

First exploit evidence seen: 2025-07-22 (earliest date across the sources below).

Exploited in the wild

• CISA KEV: listed since 2025-07-22. Source

Public exploit code

GitHub proof-of-concept repositories

7 public repositories from 7 accounts, first seen 2025-08-25. Most starred: watchtowrlabs/watchTowr-vs-CrushFTP-Authentication-Bypass-CVE-2025-54309 (28 stars), view repository.

Verify before running: public PoCs can be malicious. Read the code and only run it in an isolated lab. A PoC means exploit code is public, not that this CVE is exploited in the wild.

Sources: CISA KEV · nomi-sec/PoC-in-GitHub.

How to fix it

CISA required action

Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable. (source: CISA KEV)

Fixed versions

• crushftp crushftp: upgrade to 10.8.5 or later (affected from 10.0.0)
• crushftp crushftp: upgrade to 11.3.4_23 or later (affected from 11.0.0)

Derived from the NVD CPE configuration (versionEndExcluding / versionEndIncluding). Always confirm with the vendor advisory.

Vendor advisories and patches

• https://www.crushftp.com/crush11wiki/Wiki.jsp?page=CompromiseJuly2025 (CISA KEV notes)

MITRE ATT&CK mitigations for this chain

• M1051 Update Software (for T1068) : Update software regularly by employing patch management for internal enterprise endpoints and servers.
• M1050 Exploit Protection (for T1068) : Security applications that look for behavior used during exploitation such as Windows Defender Exploit Guard (WDEG) and the Enhanced Mitigation Experience Toolkit (EMET) can be used to mitigate some exploitation behavior. Control flow integrity checking is another way to potentially identify and stop a software exploi
• M1048 Application Isolation and Sandboxing (for T1068) : Make it difficult for adversaries to advance their operation through exploitation of undiscovered or unpatched vulnerabilities by using sandboxing. Other types of virtualization and application microsegmentation may also mitigate the impact of some types of exploitation. Risks of additional exploits and weaknesses in t
• M1019 Threat Intelligence Program (for T1068) : Develop a robust cyber threat intelligence capability to determine what types and levels of threat may use software exploits and 0-days against a particular organization.
• M1038 Execution Prevention (for T1068) : Consider blocking the execution of known vulnerable drivers that adversaries may exploit to execute code in kernel mode. Validate driver block rules in audit mode to ensure stability prior to production deployment.
• M1035 Limit Access to Resource Over Network (for T1021) : Prevent unnecessary remote access to file shares, hypervisors, sensitive systems, etc. Mechanisms to limit access may include use of network concentrators, RDP gateways, etc.
• M1047 Audit (for T1021) : Perform audits or scans of systems, permissions, insecure software, insecure configurations, etc. to identify potential weaknesses.
• M1018 User Account Management (for T1021) : Limit the accounts that may use remote services. Limit the permissions for accounts that are at higher risk of compromise; for example, configure SSH so users can only run specific programs.
• M1042 Disable or Remove Feature or Program (for T1021) : If remote services, such as the ability to make direct connections to cloud virtual machines, are not required, disable these connection types where feasible. On ESXi servers, consider enabling lockdown mode, which disables direct access to an ESXi host and requires that the host be managed remotely using vCenter.
• M1032 Multi-factor Authentication (for T1021) : Use multi-factor authentication on remote service logons where possible.

Detection Generic guidance

• Privilege Escalation: Alert on processes gaining SYSTEM/root unexpectedly, and on exploitation crashes of privileged services.
• Lateral Movement: Watch for the compromised host authenticating to other internal systems it does not normally talk to.
• Exfiltration: Watch for large or unusual outbound transfers from the affected host.

Response checklist Generic guidance

1. Inventory: find every instance of the affected product and version (include internet-facing and forgotten ones).
2. Patch or mitigate per the vendor advisory; if you cannot patch, remove internet exposure or apply the vendor workaround.
3. Assume compromise if the system was exposed before patching: hunt for the indicators in the advisory and review logs back to the disclosure date.
4. Rotate credentials and secrets stored on or used by the affected system if compromise cannot be ruled out.