CVE-2026-67191
CriticalCVSS 9.8Exploitation Probability (EPSS)
Low risk44th percentile - higher than 44% of all known CVEs
Summary
Xlight FTP Server before version 3.9.5 has a pre-authentication heap buffer overflow vulnerability. A remote unauthenticated attacker can send a malformed SSH client identification string to write past the end of a heap buffer. A logic error in the recv loop enables exploitation before authentication.
Risk Assessment
An attacker can crash the server or potentially execute arbitrary code, leading to full compromise of the FTP server.
Recommendation
Update Xlight FTP Server to version 3.9.5 or later, which includes the fix.
Other vulnerabilities in Xlight FTP Server
See all- CVE-2026-67193Medium
Xlight FTP Server before version 3.9.5 discloses the GetTickCount() value to unauthenticated attackers by sending a USER command with a username ending in :adm. Attackers can trigger the admin protocol path within the standard FTP listener pre-authentication, leaking timing information from the FTP 331 response.
- CVE-2026-67192High
Xlight FTP Server before version 3.9.5 contains a pre-authentication stack buffer overflow vulnerability. An unauthenticated attacker can send malformed SSH packets with GCM cipher negotiation, leading to stack corruption and potentially remote code execution.
- CVE-2019-25681High
Xlight FTP Server 3.9.1 has an SEH overwrite vulnerability allowing local attackers to crash the application and overwrite SEH pointers via a crafted 428-byte payload in the program execution field of virtual server configuration.
Original NVD description (English source)
Xlight FTP Server before 3.9.5 contains a pre-authentication heap buffer overflow vulnerability that allows remote unauthenticated attackers to write past the end of a heap buffer by sending a malformed SSH client identification string. A logic error in the recv loop's termination condition uses an incorrect OR operator where an AND operator is required, enabling exploitation on any SSH or SFTP connection before authentication occurs.