CVE-2026-67191
Last modified
CVE-2026-67191 is a critical-severity vulnerability rated 9.8/10 on the CVSS scale. 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.. EPSS estimates a 0.58% chance of exploitation in the next 30 days.
Description
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.
Metrics
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Weakness Enumeration
Affected Software
Source: CNA advisory (CVE.org). NVD analysis pending.
| Vendor | Product | Versions |
|---|---|---|
| Xlight | Xlight FTP Server | < 3.9.5 |
References
Timeline
- Published
- Last Modified
- Status
- Deferred
Frequently Asked Questions
What is CVE-2026-67191?
How severe is CVE-2026-67191?
How do I fix CVE-2026-67191?
How Strix Helps
- How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
- Autonomous PentestingAI agents that find and validate exploitable vulnerabilities like this one across your applications.
- PR ReviewsPentest every pull request so vulnerable code is caught before it ships to production.
- AI Penetration TestingHow AI-driven penetration testing continuously covers your attack surface.
Related CVEs from 2026
- CVE-2026-67181Rouille 0.3.3 through 3.6.2 contains an HTTP request smuggli…5.4
- CVE-2026-67182Rouille 0.3.3 through 3.6.2 contains an HTTP request smuggli…7.5
- CVE-2026-67183TinyWeb through 0.0.8 contains a memory leak vulnerability t…8.7
- CVE-2026-67184TinyWeb through 0.0.8 contains a null pointer dereference vu…8.7
- CVE-2026-67185TinyWeb through 0.0.8 contains a path traversal vulnerabilit…8.7
- CVE-2026-67188Rejected reason: This CVE ID has been rejected or withdrawn …
- CVE-2026-67192Xlight FTP Server before 3.9.5 contains a pre-authentication…9.2
- CVE-2026-67193Xlight FTP Server before 3.9.5 contains an information discl…6.9
- CVE-2026-67194Courier IMAP before 6.0.1 and Courier Mail Server before 2.0…7.1
- CVE-2026-67195Perspective 5.0.0 contains a remote code execution vulnerabi…8.8
- CVE-2026-67196Perspective 5.0.0 contains a cross-site scripting vulnerabil…5.4
- CVE-2026-67198Perspective 5.0.0 contains a denial-of-service vulnerability…8.7
Are you affected by CVE-2026-67191?
Run a free Strix scan to check your systems for this vulnerability.
Scan your code nowSource: NVD / NIST