CVE-2024-46483: Xlight FTP Server Buffer Overflow Flaw

CVE-2024-46483 Overview

CVE-2024-46483 is a critical integer overflow vulnerability affecting Xlight FTP Server versions prior to 3.9.4.3. The vulnerability exists in the packet parsing logic of the SFTP server component, where improper handling of integer values can lead to a heap overflow condition. This heap overflow can be exploited with attacker-controlled content, potentially enabling remote code execution on vulnerable systems.

Critical Impact

This vulnerability allows unauthenticated remote attackers to exploit an integer overflow in the SFTP packet parsing logic, leading to heap corruption with attacker-controlled data. This can result in complete system compromise including arbitrary code execution.

Affected Products

• Xlight FTP Server versions prior to 3.9.4.3
• Xlight FTP Server SFTP component

Discovery Timeline

• 2024-10-22 - CVE-2024-46483 published to NVD
• 2024-10-23 - Last updated in NVD database

Technical Details for CVE-2024-46483

Vulnerability Analysis

This vulnerability is classified under CWE-190 (Integer Overflow or Wraparound). The flaw resides in the SFTP server's packet parsing functionality where integer values used to calculate buffer sizes are not properly validated. When a maliciously crafted SFTP packet contains values that cause an integer overflow during size calculations, the resulting buffer allocation becomes significantly smaller than expected.

The attack can be initiated remotely over the network without requiring any authentication or user interaction. When successfully exploited, an attacker gains the ability to achieve high-impact effects across confidentiality, integrity, and availability of the affected system. This makes the vulnerability particularly dangerous for internet-facing FTP servers running vulnerable versions of Xlight.

Root Cause

The root cause is improper integer handling in the SFTP packet parsing logic. When processing SFTP packets, the server performs arithmetic operations on length fields without adequate bounds checking. If an attacker provides specially crafted length values, an integer overflow occurs, causing the server to allocate an undersized heap buffer. Subsequent write operations to this buffer overflow its boundaries, corrupting adjacent heap memory with attacker-controlled content.

Attack Vector

The attack is network-based and targets the SFTP service exposed by Xlight FTP Server. An attacker sends a specially crafted SFTP packet containing length fields designed to trigger the integer overflow condition. The attack flow proceeds as follows:

1. Attacker establishes a connection to the vulnerable SFTP service
2. Attacker sends a malformed SFTP packet with crafted length values
3. The server's packet parsing logic performs arithmetic on these values, triggering an integer overflow
4. A heap buffer is allocated with an incorrect (smaller) size
5. Packet data is written to the undersized buffer, causing heap overflow
6. Attacker-controlled data corrupts heap metadata and adjacent objects
7. This corruption can be leveraged for arbitrary code execution

For detailed technical analysis and proof-of-concept information, see the GitHub PoC Repository.

Detection Methods for CVE-2024-46483

Indicators of Compromise

• Unusual crash patterns or service restarts of the Xlight FTP Server process
• Anomalous SFTP connection patterns with malformed packet sequences
• Memory corruption artifacts in crash dumps from the Xlight FTP service
• Unexpected outbound network connections from the FTP server following SFTP sessions

Detection Strategies

• Monitor Xlight FTP Server logs for abnormal SFTP session behavior and connection failures
• Implement network intrusion detection signatures for malformed SFTP packets targeting integer overflow conditions
• Deploy endpoint detection to identify exploitation attempts through memory protection violations
• Use SentinelOne's behavioral AI to detect post-exploitation activities following heap corruption

Monitoring Recommendations

• Enable verbose logging on Xlight FTP Server to capture detailed SFTP session information
• Configure alerting on multiple rapid connection attempts to the SFTP service
• Monitor system resource utilization for signs of exploitation attempts
• Implement network traffic analysis for SFTP protocol anomalies

How to Mitigate CVE-2024-46483

Immediate Actions Required

• Upgrade Xlight FTP Server to version 3.9.4.3 or later immediately
• If immediate patching is not possible, disable the SFTP service until the update can be applied
• Restrict network access to the SFTP service to trusted IP addresses only
• Review server logs for any signs of prior exploitation attempts

Patch Information

The vendor has addressed this vulnerability in Xlight FTP Server version 3.9.4.3. Organizations should upgrade to this version or later to remediate the integer overflow vulnerability in the SFTP packet parsing logic. The patch implements proper bounds checking on integer values used in buffer size calculations.

Workarounds

• Disable the SFTP service if it is not required for business operations
• Implement network segmentation to limit exposure of the FTP server
• Deploy a Web Application Firewall (WAF) or network-based IPS with rules to filter malformed SFTP packets
• Use firewall rules to restrict SFTP access to known, trusted IP addresses only