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CVE-2026-80155 – Unauthenticated Authentication Bypass / RCE – Lantronix SLC8000, EMG8500, EMG7500,

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Summary

CVE-2026-80155 is a critical, unauthenticated authentication bypass affecting the web management portal of Lantronix out-of-band management devices, caused by a path-traversal weakness (CWE-22) in how the server handles session cookie file paths. Exploitation lets a remote, unauthenticated attacker bypass session validation, read sensitive configuration files, and upload files to arbitrary filesystem locations, which can lead to full device takeover. The vulnerability carries a maximum CVSS v3.1 base score of 10.0.

Technical details

  • Root cause: The web configuration server builds the session cookie file path using snprintf with a fixed-size buffer. Supplying a cookie value of a specific length causes the resulting path to truncate at a delimiter.
  • Trigger conditions: An attacker sends a specially-sized cookie value to the device’s web management portal; no valid session or credentials are required.
  • Attack mechanics: The truncated path is leveraged via path traversal to redirect the authentication check to an arbitrary on-disk file (such as the local user database), causing the server to bypass session validation entirely.
  • Attack vector: Network-based, no authentication or user interaction required, low attack complexity.
  • Impact: Attackers can read sensitive configuration files and upload files to arbitrary locations on the device, potentially achieving remote code execution and complete loss of confidentiality, integrity, and availability, with possible knock-on effects to serial-connected downstream devices.

Affected software

  • Lantronix SLC8000 — firmware versions before 9.7.0.5
  • Lantronix EMG8500 — firmware versions before 9.7.0.1
  • Lantronix EMG7500 — firmware versions before 9.7.0.1
  • Lantronix SLB882 — all firmware versions (no fix identified at time of writing)
  • Lantronix SLCx-03 — all firmware versions (no fix identified at time of writing)
  • Lantronix SLCx-02 — all firmware versions (no fix identified at time of writing)

Severity

  • CVSS v3.1 Base Score: 10.0 (Critical)
  • Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

Mitigation and recommended actions

  • Immediate: Upgrade Lantronix SLC8000 to firmware 9.7.0.5 or later, and EMG8500/EMG7500 to firmware 9.7.0.1 or later.
  • If no patch is available: For SLB882, SLCx-02, and SLCx-03, which have no fixed firmware at this time, restrict network access to the web management portal — place affected devices behind a firewall, remove the management interface from direct internet exposure, and limit access to trusted management networks only until a vendor patch is released.
  • Regardless of patch status, review device access logs for unexpected session or upload activity and rotate any credentials stored on or accessible from these devices.

References

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