by Kastro
Paper/Archive/CVE-2026-67191

CVE-2026-67191

Xlight Xlight FTP Server — Xlight FTP Server < 3.9.5 Pre-Auth Heap Buffer Overflow via SSH Parser

EPSS 1.0%CVSS 9.8
critical.is priorityof 100
42
CVSS 9.8 (CNA)9.8 / 10 × 3029.4Not in CISA KEV+300.0EPSS percentile 61.7.617 × 2012.3No public exploit+100.0SSVC exploitation: none+100.0
Description · from the CVE record

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.

Affected

ProductAffectedFixed inSource
Xlight FTP Server< 3.9.53.9.5CNA

Scores by source

VulnCheck (CNA)9.8CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
VulnCheck (CNA)9.3CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
CISA ADPSSVCExploitation: none · Automatable: no · Technical impact: total

References

refxlightftpd.com/whatsnew.htmwriteupvulncheck.com/advisories/xlight-ftp-server-pre-auth-heap-buffer-overflow-via-ssh-parser