CVE-2026-36779: Shenzhen Tenda Technology Co

Synopsis

Multiple stack-based buffer overflows exist in the Tenda O3 Wireless Router (firmware v1.0.0.5(4180)), specifically in the fromVirtualSer function, reachable via five distinct input parameters. The vulnerabilities are exploitable remotely over the network without any authentication or user interaction. Successful exploitation crashes the router, causing a denial of service by exhausting the call stack. 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 reach the router's HTTP service over the network; no local or physical access is needed.

• AuthenticationNot required

  No credentials or session token are needed to send the malicious HTTP request that triggers the overflow.

• Victim interactionNot required

  The exploit is delivered entirely by the attacker; no user on the target device needs to click, browse, or approve anything.

• Attack complexityDetail

  Exploitation is reliable and condition-free; no race conditions, memory-layout knowledge, or special environmental state is required.

Blast Radius

• The targeted router process crashes, dropping all active network connections routed through the device.
• The denial of service persists until the device is manually rebooted or power-cycled, as the overflowed stack frame cannot self-recover.
• Any services or hosts depending on the router for connectivity (VPN tunnels, virtual server mappings) become unreachable for the duration of the outage.