CVE-2024-48208: Pure-FTPd Buffer Overflow Vulnerability

CVE-2024-48208 Overview

CVE-2024-48208 is an Out-of-Bounds Read vulnerability affecting Pure-FTPd versions prior to 1.0.52. The vulnerability exists in the domlsd() function within the ls.c file, where improper boundary checking allows an attacker to read memory beyond the intended buffer limits. This memory corruption vulnerability can be exploited remotely over the network without authentication, potentially leading to information disclosure, data integrity issues, and service disruption.

Critical Impact

Remote attackers can exploit this out-of-bounds read vulnerability in Pure-FTPd to cause denial of service conditions and potentially leak sensitive memory contents from the FTP server process.

Affected Products

• Pure-FTPd versions prior to 1.0.52
• All installations running vulnerable Pure-FTPd releases

Discovery Timeline

• 2024-10-24 - CVE-2024-48208 published to NVD
• 2025-09-04 - Last updated in NVD database

Technical Details for CVE-2024-48208

Vulnerability Analysis

This vulnerability is classified as CWE-125 (Out-of-bounds Read), which occurs when software reads data past the end or before the beginning of an intended buffer. In the context of Pure-FTPd, the flaw resides specifically in the domlsd() function responsible for handling machine-readable directory listing (MLSD) operations in the ls.c source file.

When a client requests a directory listing, the domlsd() function processes the request and formats the output. Due to insufficient bounds checking, the function can read beyond allocated buffer boundaries when handling certain input conditions. This can result in the server accessing unintended memory regions, potentially exposing sensitive data from adjacent memory locations or causing the service to crash.

The network-accessible nature of FTP services means this vulnerability can be triggered remotely by any client that can establish a connection to the FTP server, without requiring prior authentication credentials.

Root Cause

The root cause of CVE-2024-48208 is inadequate boundary validation in the domlsd() function within ls.c. The function fails to properly verify that read operations remain within the bounds of allocated buffers before accessing memory. This programming error allows read operations to extend beyond the legitimate data boundary, accessing adjacent memory regions that may contain sensitive information or invalid data.

Attack Vector

The attack vector for this vulnerability is network-based, allowing remote exploitation. An attacker can exploit this vulnerability by:

1. Establishing a connection to the vulnerable Pure-FTPd server
2. Issuing MLSD (Machine Listing Directory) commands crafted to trigger the out-of-bounds read condition
3. The malformed request causes the domlsd() function to read beyond buffer boundaries
4. This can result in information leakage, unexpected server behavior, or denial of service

The vulnerability does not require user interaction and can be exploited without authentication, making it accessible to any network attacker who can reach the FTP service.

Detection Methods for CVE-2024-48208

Indicators of Compromise

• Unexpected Pure-FTPd service crashes or restarts, particularly during directory listing operations
• Abnormal memory usage patterns in the Pure-FTPd process
• Unusual MLSD command patterns in FTP server logs
• Segmentation faults or memory access violations in system logs related to pure-ftpd

Detection Strategies

• Monitor FTP server logs for unusual MLSD command activity or malformed directory listing requests
• Implement intrusion detection rules to flag suspicious FTP traffic patterns targeting directory listing functions
• Deploy memory protection mechanisms such as ASLR and stack canaries to help detect exploitation attempts
• Use version detection scanning to identify Pure-FTPd installations running versions prior to 1.0.52

Monitoring Recommendations

• Enable verbose logging on Pure-FTPd servers to capture detailed command activity
• Configure alerting for unexpected service terminations or memory-related errors in the FTP daemon
• Implement network monitoring to detect anomalous FTP traffic volumes or command sequences
• Regularly audit installed Pure-FTPd versions across the infrastructure to ensure timely patching

How to Mitigate CVE-2024-48208

Immediate Actions Required

• Upgrade Pure-FTPd to version 1.0.52 or later immediately on all affected systems
• If immediate patching is not possible, consider restricting network access to FTP services using firewall rules
• Enable additional logging to monitor for potential exploitation attempts
• Review and limit access to FTP services to only authorized clients and networks

Patch Information

The vulnerability has been addressed in Pure-FTPd version 1.0.52. The fix is documented in GitHub Pull Request #176 for pure-ftpd, which corrects the boundary checking in the domlsd() function. Administrators should upgrade to version 1.0.52 or later to remediate this vulnerability.

Workarounds

• Restrict FTP server access to trusted IP addresses using firewall rules or Pure-FTPd's built-in access controls
• Consider disabling MLSD command support if not required for your FTP use case
• Deploy a web application firewall (WAF) or network intrusion prevention system (IPS) with rules to detect and block malicious FTP traffic
• Run Pure-FTPd in a containerized or sandboxed environment to limit the impact of potential exploitation

# Configuration example: Restrict FTP access using iptables
# Allow FTP only from trusted network
iptables -A INPUT -p tcp --dport 21 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 21 -j DROP

# Or use Pure-FTPd's built-in IP restrictions
# Edit /etc/pure-ftpd/conf/IPRestrictions
# Add allowed IP ranges