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CVE-2026-101077 – Unauthenticated Arbitrary File Write / RCE Chain – Netcore NR289-GE 1.4.5102

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Summary

CVE-2026-101077 is a missing-authentication (CWE-306) vulnerability in the process_request function of the boa_temp handler in the embedded boa web server used by the Netcore NR289-GE router, firmware version 1.4.5102. The flaw allows an unauthenticated remote attacker to write arbitrary content to fixed staging files on the device, which feed into the firmware upgrade and configuration-restore processes. The vulnerability has a maximum CVSS v3.1 base score of 10.0 (Critical) and a public exploit is available.

Technical details

  • Root cause: the router’s boa binary inspects the URL path of incoming POST requests for the substrings update/upgrade or para_recover. If matched, it opens a fixed file (/tmp/boa_temp.update or /tmp/boa_temp.para) and streams the raw POST body into it, with no authentication, size limit, or content validation.
  • Trigger conditions: any POST request whose path contains one of the matched substrings is processed by this logic, regardless of session state or credentials. Public PoC combines this with a separate .ico extension whitelist flaw to reach the handler without any authentication at all.
  • Attack vector: Network — a single unauthenticated HTTP POST request (e.g., POST /x.ico/firmware_upgrade) is sufficient; the HTTP response (typically 404) does not reflect the fact that the file has already been written server-side.
  • Impact: /tmp/boa_temp.update is later moved to /tmp/upgrade and consumed by the device’s AP/firmware upgrade flow, allowing an attacker to corrupt or plant content in the upgrade channel (denial of service; further impact is bounded by an RSA signature check). /tmp/boa_temp.para is consumed by the configuration-restore flow, which only validates a device-model string in the header, allowing a crafted configuration blob (including web credentials) to be staged for restoration onto the device.

Affected software

  • Netcore NR289-GE router firmware version 1.4.5102 (build 2018.06.14)

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: No vendor patch is currently available — Netcore was contacted about this disclosure and did not respond. Contact Netcore support directly to request a firmware update addressing this issue.
  • If no patch: Restrict management/web-interface access on the router to trusted internal networks only, and disable remote/WAN administration. Block or firewall unauthenticated POST requests to the device’s web server where feasible, and monitor for unexpected writes/changes tied to firmware-upgrade or configuration-restore activity. Given the lack of vendor response, organizations should evaluate replacing affected devices in security-sensitive deployments.

References

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