What is CVE-2026-109439?

CVE-2026-109439 is a critical-severity vulnerability in Lantronix Xpress-Dr, classified under Missing Authentication for Critical Function. CVSS score: 9.8/10. Published 2026-10-14.

How severe is CVE-2026-109439?

Critical severity. CVSS v3 base score is 9.8 out of 10.

Auth bypass in Lantronix Xpress-Dr

CVE-2026-109439

Lantronix XPress-DR and XPress-DR-I (CoBos-family) firmware through 8.1.0.0 contains a missing authentication vulnerability that allows remote attackers to read and persistently overwrite device configuration by sending crafted frames to the unauthenticated UDP configuration protocol on port 30718. Attackers can send a type 0xF8 query to read live configuration data and a type 0xFD frame with exactly 0x78 body bytes to rewrite the device IP address and serial-channel forwarding records, causing changes to commit to EEPROM and persist across reboots. The XPress-DR product series reached end-of-life/end-of-support in February 2025.

Vulnerability class: Broken Authentication

Published 2026-10-14.

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.

Affected products

Weakness classification (CWE)

CWE-306 — Missing Authentication for Critical Function

References

cdn.lantronix.com/wp-content/uploads/pdf/PCN-753-Rev-B-EOL-Notice-XPRESS.pdf (vendor-advisory)
www.vulncheck.com/advisories/lantronix-xpress-dr-unauthenticated-configuration-… (third-party-advisory)

Frequently asked questions

What is CVE-2026-109439?: CVE-2026-109439 is a critical-severity vulnerability in Lantronix Xpress-Dr, classified under Missing Authentication for Critical Function. CVSS score: 9.8/10. Published 2026-10-14.
How severe is CVE-2026-109439?: Critical severity. CVSS v3 base score is 9.8 out of 10.