CrushFTP: Stop CVE-2024-4040 Exploitation

Protect Kubernetes workloads from unauthorized access and exploitation attempts by using AccuKnox Runtime Security to block CVE-2024-4040 attacks.

The recently discovered CVE-2024-4040 vulnerability in CrushFTP exposes serious risks to organizations relying on this popular file transfer platform. Rated with a CVSS score of 9.8, this flaw allows unauthenticated attackers to bypass CrushFTP’s Virtual File System (VFS) sandbox protections and access sensitive files through a server-side template injection (SSTI) vulnerability.

In cloud-native environments where CrushFTP is deployed on Kubernetes, this vulnerability could lead to remote code execution (RCE), privilege escalation, and lateral movement across clusters, causing major data breaches or service disruptions.

In this demonstration, we simulate the CVE-2024-4040 attack in a Kubernetes cluster and show how AccuKnox Runtime Security can block the exploitation attempt in real time by enforcing file-level access control policies.

Step-by-Step Guide: Blocking the CrushFTP CVE-2024-4040 Attack Using AccuKnox Runtime Security

• Deploy a vulnerable CrushFTP instance in a Kubernetes cluster and expose it publicly through a NodePort service (for example, port 30036), creating an attack surface for the simulation.
  
• Use a publicly available proof-of-concept (PoC) script to exploit CVE-2024-4040. This PoC extracts sensitive files such as /etc/passwd from the CrushFTP server, demonstrating successful unauthorized access.
  
• Onboard the Kubernetes cluster into the AccuKnox CNAPP platform, ensuring that runtime security monitoring is fully enabled across workloads.
  
• Navigate to Runtime Protection > Policy in the AccuKnox dashboard, select the onboarded cluster, and choose the correct namespace where the vulnerable CrushFTP pod is running.
  
• Create a new runtime security policy by either using the built-in Policy Editor or uploading a YAML policy under the "Custom" tab.
  
• Apply a hardening policy that blocks file read operations to critical paths such as /etc/passwd, /etc/shadow, /var/log/auth.log, /var/log/wtmp, and /var/run/utmp, which are commonly targeted during exploitation attempts.
  
• Simulate the exploit attempt again after the policy is applied, using the same PoC script. Notice that attempts to access sensitive files are now denied, preventing data leakage or further compromise.
  
• Go to Monitor > Alerts in the AccuKnox platform to view logs of blocked access attempts. These alerts capture full forensic details, including the violating process, source container, namespace, action taken, and severity level.
  
• Inspect individual alerts to confirm that CrushFTP’s unauthorized file access was successfully blocked in real time, demonstrating that AccuKnox effectively mitigated the vulnerability.
  
• Maintain active runtime protection by keeping these granular file-level policies enforced across critical workloads, ensuring continuous defense against CVE-2024-4040 exploitation and similar threats.
  

How CVE-2024-4040 Threatens Kubernetes Workloads

Exploiting CVE-2024-4040 in Kubernetes deployments can result in:

• Unauthenticated Remote Code Execution (RCE) within vulnerable containers.
  
• Privilege Escalation that attackers can leverage to access other parts of the cluster.
  
• Lateral Movement to other pods, services, or namespaces, expanding the attack blast radius.
  

Without runtime protections in place, even a single vulnerable container could jeopardize the entire Kubernetes environment, exposing sensitive applications, data, and credentials.

How AccuKnox Runtime Security Defends Against Exploitation

AccuKnox’s KubeArmor-based Runtime Security leverages eBPF and Linux Security Modules (LSMs) like AppArmor and SELinux to enforce strict, kernel-level security controls, including:

• Granular File Access Controls: Policies precisely control which processes can access which files and directories inside containers.
  
• Real-Time Exploit Blocking: Unauthorized file access attempts are immediately blocked at the system call level — no application code changes required.
  
• Detailed Monitoring and Alerting: Every blocked attempt is logged with actionable details to support incident response and forensics.
  
• Zero Trust Policy Enforcement: Only explicitly allowed behaviors are permitted, significantly reducing the attack surface.
  

Through proactive runtime defense, AccuKnox ensures that known and unknown exploits targeting Kubernetes applications are stopped before they cause real damage.

Stop Critical Exploits Like CVE-2024-4040 with AccuKnox

CVE-2024-4040 is a stark reminder that even trusted applications like CrushFTP can become significant threats when vulnerabilities are left unprotected.

By combining real-time policy enforcement, kernel-native runtime monitoring, and automated incident detection, AccuKnox Runtime Security empowers organizations to:

• Stop exploitation before attackers gain a foothold.
  
• Maintain strong Kubernetes workload isolation.
  
• Achieve continuous compliance with Zero Trust security principles.
  

Don’t wait for breaches to expose your cloud infrastructure.
Secure your Kubernetes clusters today with AccuKnox Runtime Security.