CVE-2024-46483 Overview
CVE-2024-46483 is an integer overflow vulnerability in Xlight FTP Server versions prior to 3.9.4.3. The flaw resides in the packet parsing logic of the SFTP server component. An integer overflow during length calculation allows attackers to trigger a subsequent heap overflow with attacker-controlled content. Remote unauthenticated attackers can exploit this issue over the network without user interaction. The vulnerability is classified under CWE-190 (Integer Overflow or Wraparound). A public proof-of-concept exists in the GitHub PoC Repository, increasing the likelihood of exploitation against exposed servers.
Critical Impact
Unauthenticated remote attackers can corrupt heap memory in the Xlight SFTP service, enabling potential remote code execution and full server compromise.
Affected Products
- Xlight FTP Server versions prior to 3.9.4.3
- SFTP service component of Xlight FTP Server
- Windows hosts running vulnerable Xlight FTP Server installations
Discovery Timeline
- 2024-10-22 - CVE-2024-46483 published to NVD
- 2026-04-15 - Last updated in NVD database
Technical Details for CVE-2024-46483
Vulnerability Analysis
The vulnerability resides in how the Xlight SFTP server parses incoming packets. SFTP packets contain length-prefixed fields that the server must validate before allocating buffers. The packet parsing logic performs arithmetic on attacker-supplied size values without proper bounds checking. When the calculation wraps around the integer maximum, the server allocates a smaller buffer than required for the inbound data. Subsequent copy operations write attacker-controlled bytes past the allocated heap region.
This primitive corrupts adjacent heap metadata and object pointers in the SFTP server process. Attackers who control the overflowed content can manipulate heap structures to achieve arbitrary write conditions. Successful exploitation grants code execution in the context of the FTP service account.
The attack vector is network-accessible and requires no authentication or user interaction. The EPSS score of 13.894% places this CVE in the 94th percentile for predicted exploitation likelihood.
Root Cause
The root cause is missing validation of arithmetic operations on untrusted length fields parsed from SFTP packets. The code path computes an allocation size using attacker-controlled integers, allowing the result to wrap. This integer overflow violates the size invariant expected by the downstream memory copy routine.
Attack Vector
An attacker establishes a TCP connection to the SFTP listener on the vulnerable Xlight FTP Server. The attacker sends a crafted SFTP packet with length fields engineered to trigger the arithmetic wraparound. The server allocates an undersized heap buffer and copies attacker-controlled payload data into it, producing a heap overflow. Public exploitation details are available in the kn32 PoC repository.
Detection Methods for CVE-2024-46483
Indicators of Compromise
- Unexpected crashes or restarts of the xlight.exe process or Xlight FTP service
- SFTP sessions originating from untrusted IP ranges that disconnect abruptly after sending malformed packets
- Child processes spawned by the Xlight FTP service that are not part of normal operation
- Outbound network connections from the FTP server host to unexpected external IP addresses following an SFTP session
Detection Strategies
- Monitor SFTP traffic for malformed packet length fields and oversized payload claims that do not match transferred bytes
- Enable application crash logging on the host and alert on faults within the Xlight process
- Inspect Windows Event Logs for service restart events tied to the FTP service
- Correlate SFTP authentication failures and pre-authentication packet anomalies from the same source address
Monitoring Recommendations
- Place Xlight FTP Server behind network sensors capable of decoding SSH/SFTP framing for anomaly identification
- Forward host telemetry to a centralized data lake to correlate process crashes with network sessions
- Track outbound connections originating from the FTP server process to identify post-exploitation command-and-control
- Baseline normal SFTP client behavior and alert on deviations in packet sizes and session timing
How to Mitigate CVE-2024-46483
Immediate Actions Required
- Upgrade Xlight FTP Server to version 3.9.4.3 or later on all affected hosts
- Restrict SFTP service exposure to trusted source IP ranges using host or perimeter firewalls
- Audit FTP server hosts for signs of prior exploitation, including unexpected processes and persistence artifacts
- Rotate credentials and keys stored on or accessible from compromised FTP server hosts
Patch Information
Xlight FTP Server version 3.9.4.3 addresses the integer overflow in the SFTP packet parsing logic. Administrators should obtain the updated build from the vendor and validate the installed version after upgrade. Refer to the GitHub PoC Repository for technical details on the vulnerable code path.
Workarounds
- Disable the SFTP listener if only FTP or FTPS protocols are required for business operations
- Bind the SFTP service to internal interfaces only and require VPN access for remote users
- Place the FTP server behind a reverse proxy or jump host that terminates and validates SSH/SFTP sessions
- Apply rate limiting on the SFTP port to slow brute-force exploitation attempts against the listener
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
