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CVE-2026-16876 – Authentication Bypass / Arbitrary Command Execution – NEC UNIVERGE IX-R/IX-V Router

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Summary

CVE-2026-16876 is a critical missing-authentication vulnerability (CWE-306) affecting NEC’s UNIVERGE IX-R/IX-V series enterprise routers. A remote, unauthenticated attacker can send a specially crafted message to the device’s WebGUI to bypass authentication and execute arbitrary CLI commands. The flaw carries a CVSS v3 base score of 9.4 (Critical) and requires no user interaction or privileges to exploit.

Technical details

  • Root cause: The WebGUI of affected UNIVERGE IX-R/IX-V firmware fails to properly enforce authentication for a critical function, allowing WebGUI messages to be tampered with.
  • Trigger conditions: An attacker sends a specially crafted request/message to the exposed WebGUI service (HTTP/HTTPS) without needing valid credentials.
  • Attack vector: Network — exploitable remotely against any device with the WebGUI reachable, with low attack complexity and no privileges or user interaction required.
  • Impact: Successful exploitation allows the attacker to bypass authentication entirely and execute arbitrary CLI commands on the router, potentially leading to full device compromise, traffic interception/manipulation, and use of the router as a pivot point into the internal network.
  • Discovery: Reported by Kojiro Enokida (SOPHOS) and coordinated through JPCERT/CC and IPA under Japan’s Information Security Early Warning Partnership; published via JVN and NEC’s own security advisory.

Affected software

  • NEC UNIVERGE IX-R/IX-V series (including IX-R2510, IX-R2520, IX-R2530, IX-R2610-4G, and IX-V100)
  • Firmware Ver1.1 – Ver1.3
  • Firmware Ver1.4.21 – Ver1.4.28
  • Firmware Ver1.5.23

Severity

  • CVSS v3.1 Base Score: 9.4 (Critical)
  • Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L
  • A CVSS v4.0 score of 9.3 has also been assigned (CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:L/SC:N/SI:N/SA:N).

Mitigation and recommended actions

  • Immediate: Update affected UNIVERGE IX-R/IX-V devices to the vendor-fixed firmware versions (Ver1.4.34 and Ver1.5.29, as referenced in public reporting on this advisory).
  • If patching is not immediately possible:
    • Disable the WebGUI on affected devices until the update can be applied.
    • Stop the HTTP(S) server function if the WebGUI is not required.
    • Restrict access to the management interface via source-IP filtering/ACLs so it is only reachable from trusted management networks.
    • Avoid exposing the WebGUI on default ports or to the public internet; use non-default TCP ports and network segmentation to reduce discoverability.
  • Monitor router logs and network traffic for unexpected CLI command execution or configuration changes as an indicator of exploitation attempts.

References

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