CVE-2026-10120: TRENDnet TEW-432BRP formSetFirewallRule stack-based overflow

Synopsis

A stack-based buffer overflow exists in the formSetFirewallRule handler (/goform/formSetFirewallRule) of the TRENDnet TEW-432BRP router running firmware 3.10B20, triggered by an oversized firewall_name argument. The bug is reachable over the network by any authenticated user, and successful exploitation lets an attacker corrupt stack memory to achieve code execution or persistent compromise of the device, fully impacting confidentiality, integrity, and availability. The product has been end-of-life since 2009 and the vendor has stated it will not issue a fix; HarborGuard tracks the advisory for any future patch availability.

HarborGuard Coverage

Exploit Conditions

• Network reachabilityRequired

  The attacker must reach the router's HTTP management interface over the network (AV:N).

• AuthenticationRequired

  A low-privilege account on the device web UI is sufficient to invoke the vulnerable handler (PR:L).

• Victim interactionNot required

  No user action is needed; the attacker drives the request directly (UI:N).

• Attack complexityDetail

  Attack complexity is low and the exploit is public, making it reliable and condition-free (AC:L, E:P).

Blast Radius

• Overwrites the stack of the embedded HTTP server process, enabling arbitrary code execution on the router.
• Reads stored device configuration, including firewall rules, credentials, and any cached secrets.
• Modifies persisted device settings such as DNS, routing, and firewall policy, enabling traffic interception or redirection.
• Crashes or bricks the management daemon, taking the router offline for users behind it.