1. Introduction
The ArGoSoft FTP Server DELE Command Remote Buffer Overrun vulnerability allows a malicious user with delete rights to execute code on the server by sending a specially crafted DELE command exceeding 2000 characters. This could allow an attacker to gain control of the affected system, potentially leading to data theft or service disruption. Systems running ArGoSoft FTP Server are typically at risk. A successful exploit may compromise confidentiality, integrity and availability.
2. Technical Explanation
The vulnerability is a heap-based buffer overflow in the handling of DELE commands within ArGoSoft FTP Server. An attacker can trigger this by providing an argument longer than 2000 characters to the DELE command, overwriting adjacent memory and potentially executing arbitrary code. The CVE associated with this issue is CVE-2005-0696.
- Root cause: Insufficient input validation on the length of the filename provided in a DELE command.
- Exploit mechanism: An attacker connects to the FTP server, authenticates with an account possessing delete privileges, and sends a DELE command containing a string longer than 2000 characters. This overflows a buffer on the heap, potentially allowing for arbitrary code execution.
- Scope: ArGoSoft FTP Server versions affected are not explicitly specified in the available information but are known to include those identifying as vulnerable based on banner grabbing.
3. Detection and Assessment
You can confirm if a system is vulnerable by checking the server’s banner string for the ArGoSoft FTP Server version. Scanning tools may also identify this vulnerability using specific signatures.
- Quick checks: Connect to the FTP server via command line and check the banner. For example, use
ftp <target_ip>then enter a username/password if required. The banner will display the version information. - Scanning: Nessus plugin ID 12755 may detect this vulnerability. Other scanners may have similar signatures.
- Logs and evidence: Examine FTP server logs for unusually long DELE commands or errors related to buffer overflows. Log locations vary depending on configuration, but common paths include /var/log/ftpd or the application’s installation directory.
ftp <target_ip>
User (anonymous): <username>
Password: <password>
220 ArGoSoft FTP Server 1.x ready...
4. Solution / Remediation Steps
At this time, a specific solution or patch is not known to be available for this vulnerability. Mitigation focuses on limiting access and monitoring.
4.1 Preparation
- Services: No services need to be stopped.
- Rollback plan: Restore the system from the pre-change backup if issues occur. Change window approval may be needed depending on your organisation’s policy.
4.2 Implementation
- Step 1: Restrict delete access to only authorized users and accounts. Review user permissions and remove unnecessary delete privileges.
- Step 2: Implement strict monitoring of FTP server logs for suspicious activity, particularly long DELE commands or errors related to buffer overflows.
4.3 Config or Code Example
Before
#Example user configuration allowing delete access (this is a placeholder)
user <username> {
permissions: all
}
After
#Example user configuration restricting delete access (this is a placeholder)
user <username> {
permissions: read, write
}
4.4 Security Practices Relevant to This Vulnerability
- Least privilege: Granting users only the minimum necessary permissions reduces the potential impact of an exploit.
- Input validation: Validating user input on both the client and server side can prevent malicious data from being processed.
4.5 Automation (Optional)
No automation is available at this time.
5. Verification / Validation
- Post-fix check: Attempt to connect to the FTP server as an unauthorized user and issue a DELE command with a string longer than 2000 characters. The command should fail with an access denied or similar error.
- Re-test: Re-run the banner check from section 3 to confirm the ArGoSoft FTP Server version is still present, then attempt the unauthorized DELE command again.
- Smoke test: Verify that authorized users can still connect and perform read/write operations on the server.
- Monitoring: Monitor FTP server logs for any errors related to access denied or invalid input.
ftp <target_ip>
User (unauthorized): <username>
Password: <password>
530 Login incorrect
6. Preventive Measures and Monitoring
- Baselines: Update security baselines to include restrictions on FTP server access and permissions.
- Pipelines: Implement input validation checks in any custom scripts or applications that interact with the FTP server.
- Asset and patch process: Regularly review asset inventories and apply available patches promptly, although a specific patch is not currently known for this vulnerability.
7. Risks, Side Effects, and Roll Back
- Roll back: Restore the system from the pre-change backup to revert any modifications made to user permissions.
8. References and Resources
- Vendor advisory or bulletin: No official vendor advisory is available at this time.
- NVD or CVE entry: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2005-0696
- Product or platform documentation relevant to the fix: https://www.securityfocus.com/archive/1/archive/1/426081/100/0/threaded