CVE-2026-36783: Shenzhen Tenda Technology Co

Synopsis

A stack-based buffer overflow in the Tenda O3 Wireless Router (firmware v1.0.0.5(4180)) allows a remote attacker to crash the device by sending a crafted HTTP request with an oversized value in the domain parameter of the fromNetToolGet function. The vulnerability is reachable over the network with no authentication required and no user interaction needed. Successful exploitation causes a denial of service, taking the router offline until it is manually rebooted or resets itself. HarborGuard is tracking this advisory and will make a patched-image rebuild available as soon as an upstream fix is published.

HarborGuard Coverage

Exploit Conditions

• Network reachabilityRequired

  The attacker must be able to reach the router's HTTP service over the network; no local or physical access is required.

• AuthenticationNot required

  The vulnerable endpoint accepts unauthenticated requests, so no account or credential is needed to trigger the overflow.

• Victim interactionNot required

  The attacker sends a crafted HTTP request directly to the device; no user on the target device needs to click or open anything.

• Attack complexityDetail

  Attack complexity is low, meaning the exploit is reliable and requires no special timing, race conditions, or environmental prerequisites beyond network access.

Blast Radius

• The router process crashes, dropping all network connectivity for every device behind or through the affected O3 router.
• Recovery requires a manual reboot or automatic watchdog restart, creating a window of complete network unavailability.
• Repeated exploitation can keep the device in a continuous crash-restart loop, sustaining the outage indefinitely.