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CVE-2026-74843 – Unauthenticated RCE via Stack Buffer Overflow – WAVLINK WN531P3 / WN535M1 (V250922)

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Summary

CVE-2026-74843 is a critical, unauthenticated stack-based buffer overflow affecting the WAVLINK WN531P3 and WN535M1 router web management interfaces (firmware V250922). The flaw resides in the Export Pingortrace CGI component and can be triggered remotely over the network with no authentication, potentially leading to arbitrary code execution on the device. It carries the maximum CVSS v3.1 base score of 10.0.

Technical details

  • Root cause: The export_pingortrace.cgi script at /etc/lighttpd/www/cgi-bin/export_pingortrace.cgi uses strcpy to copy the value of the HTTP_COOKIE header into a fixed-size stack buffer without length validation.
  • Trigger: An attacker sends a crafted HTTP request to the CGI endpoint with an oversized HTTP_COOKIE value.
  • Attack vector: Network-based, no authentication or user interaction required.
  • Impact: Stack memory corruption that can crash the device or be leveraged for remote code execution, with full compromise of confidentiality, integrity, and availability.

Affected software

  • WAVLINK WN531P3 — firmware version V250922
  • WAVLINK WN535M1 — firmware version V250922

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: Check with WAVLINK for updated firmware beyond V250922 for the WN531P3 and WN535M1 models and apply it as soon as it is available. No confirmed vendor patch has been identified at time of writing.
  • If no patch is available: Do not expose the router’s web management interface (including CGI endpoints under /cgi-bin/) to the public internet; restrict access to trusted internal networks only, disable remote/WAN administration, and place the device behind a firewall or VPN. Monitor for anomalous HTTP requests containing unusually long Cookie header values targeting export_pingortrace.cgi.

References

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