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CVE-2026-75784 – Remote Stack-Based Buffer Overflow (RCE) – TRENDnet TEW-WLC100 firmware 1v2.07b01

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Summary

CVE-2026-75784 is a critical, unauthenticated stack-based buffer overflow affecting the TRENDnet TEW-WLC100 wireless LAN controller running firmware version 1v2.07b01. The flaw resides in the device’s embedded nginx HTTP server, specifically in the function handling the HTTP Server request header, and can be triggered remotely over the network with no authentication or user interaction. Given the network attack vector and the potential for full compromise of confidentiality, integrity, and availability, this vulnerability has been assigned a maximum CVSS v3.1 base score of 10.0.

Technical details

  • Root cause: The nginx binary shipped with the TEW-WLC100 (/usr/nginx/sbin/nginx) contains a function (identified in decompiled analysis as FUN_0040da4c) that copies attacker-controlled input from the HTTP Server header into a fixed-size stack buffer without proper bounds checking.
  • Trigger conditions: Sending a crafted HTTP request to the device’s web management service with an oversized/malformed Server header value overflows the stack buffer.
  • Attack vector: Network-based (AV:N) — no authentication (PR:N) and no user interaction (UI:N) are required, meaning any attacker with network access to the device’s HTTP interface can exploit it.
  • Impact: Successful exploitation overwrites the stack, including the return address, enabling arbitrary code execution on the device. This can lead to full device takeover, disruption of wireless LAN controller services, and use of the device as a pivot point into the internal network.
  • Weakness classification: CWE-121 (Stack-based Buffer Overflow) and CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer).
  • A public proof-of-concept exploit is available that demonstrates overwriting the saved return address via a crafted Server header, confirming practical exploitability.

Affected software

  • TRENDnet TEW-WLC100, firmware version 1v2.07b01

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 or firmware update addressing this specific CVE has been identified as of the time of writing. TRENDnet’s last published firmware for this model (V2.08b01, released 2020) predates this disclosure and does not reference this vulnerability. Organizations should check TRENDnet’s support page for any newer firmware release addressing this issue before deploying it.
  • If no patch is available:
    • Remove the device’s web management (HTTP) interface from direct internet exposure; restrict access to trusted management networks only.
    • Place the device behind a firewall or VPN and restrict inbound access to the HTTP management port to known administrative hosts.
    • Monitor for anomalous HTTP requests containing abnormally long or malformed Server headers targeting the device.
    • Given the TEW-WLC100 appears to be an end-of-life product with no recent security updates, evaluate replacing it with an actively supported wireless LAN controller.

References

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