CVE-2026-10158 Overview
CVE-2026-10158 is a stack-based buffer overflow in the TRENDnet TEW-432BRP wireless router running firmware version 3.10B20. The flaw resides in the formPortFw function handler at /goform/formPortFw, where the server_name parameter is copied into a fixed-size stack buffer without bounds checking [CWE-119]. An authenticated remote attacker can send a crafted HTTP request to corrupt the stack and influence execution flow. The exploit has been published, and TRENDnet has confirmed the device reached end-of-life (EOL) in 2009 and will not receive a fix.
Critical Impact
Remote attackers with low privileges can trigger stack memory corruption on EOL TRENDnet TEW-432BRP routers, potentially leading to arbitrary code execution or device compromise with no vendor patch available.
Affected Products
- TRENDnet TEW-432BRP firmware version 3.10B20
- The formPortFw handler at /goform/formPortFw
- End-of-life since 2009 — no supported version exists
Discovery Timeline
- 2026-05-31 - CVE-2026-10158 published to NVD
- 2026-06-01 - Last updated in NVD database
Technical Details for CVE-2026-10158
Vulnerability Analysis
The vulnerability exists in the web management interface of the TRENDnet TEW-432BRP router. The formPortFw function processes port-forwarding configuration submissions sent to /goform/formPortFw. When the handler reads the server_name HTTP parameter, it copies the attacker-controlled value into a fixed-size stack buffer using an unsafe string operation. No length validation is performed before the copy.
An attacker who can authenticate to the web interface — or reach an already-authenticated session — can submit an oversized server_name value. The overflow overwrites adjacent stack data, including saved return addresses on the MIPS-based firmware. On embedded devices without stack canaries, address space layout randomization (ASLR), or non-executable stacks, this typically permits reliable control of execution flow.
A public proof-of-concept has been released through GitHub Exploit Documentation and tracked in VulDB Vulnerability #367411.
Root Cause
The root cause is missing input length validation on the server_name request parameter before it is copied into a stack-allocated buffer inside formPortFw. The function relies on unbounded string copy semantics rather than length-checked alternatives, producing a classic memory corruption condition classified under [CWE-119] (Improper Restriction of Operations within the Bounds of a Memory Buffer).
Attack Vector
Exploitation requires network access to the router's administrative HTTP interface and valid low-privilege credentials. The attacker submits a POST request to /goform/formPortFw containing an overlong server_name field. Because routers commonly retain default or weak credentials, and management interfaces are sometimes exposed beyond the LAN, the practical attack surface can be significant for any TEW-432BRP still in deployment.
No verified exploit code is reproduced here. Refer to the GitHub Exploit Documentation and VulDB CTI for #367411 for technical details.
Detection Methods for CVE-2026-10158
Indicators of Compromise
- HTTP POST requests to /goform/formPortFw containing unusually long server_name parameter values
- Router reboots, web UI crashes, or unresponsive management interface following configuration changes
- Unexpected firmware behavior, new port-forwarding rules, or DNS configuration changes on TEW-432BRP devices
- Outbound connections from the router to unknown command-and-control infrastructure
Detection Strategies
- Inspect HTTP traffic destined for router management interfaces and flag requests where server_name exceeds expected length (typically 64 bytes or less)
- Apply network intrusion detection signatures matching POST requests to /goform/formPortFw with oversized form fields
- Audit network inventory to identify any TRENDnet TEW-432BRP devices still operating, including those behind NAT or in branch offices
Monitoring Recommendations
- Log and review all administrative access attempts to legacy router web interfaces
- Monitor DNS and outbound traffic patterns from network gateways for signs of router compromise
- Alert on configuration changes to port forwarding, DNS, or firewall rules on edge devices
How to Mitigate CVE-2026-10158
Immediate Actions Required
- Replace the TRENDnet TEW-432BRP with a vendor-supported router that receives security updates
- Block external access to the router's HTTP administration interface and restrict it to a trusted management VLAN
- Change default and weak administrative credentials, then disable remote management if it cannot be removed
- Segment any TEW-432BRP that cannot be replaced immediately so it cannot reach sensitive internal assets
Patch Information
No patch is available. TRENDnet has stated the TEW-432BRP has been EOL since 2009 and the vendor will not investigate or remediate this issue. Continued use should be treated as accepting unmitigated risk.
Workarounds
- Disable port-forwarding configuration access for non-administrative users on the device
- Place the router behind a separate, supported firewall and disable its WAN-side management entirely
- Apply ACLs on upstream switches or firewalls to restrict who can reach /goform/formPortFw
- Plan and execute device replacement as the only durable mitigation
# Example firewall rule to restrict router admin access to a single management host
iptables -A FORWARD -p tcp -d <router_ip> --dport 80 -s <mgmt_host_ip> -j ACCEPT
iptables -A FORWARD -p tcp -d <router_ip> --dport 80 -j DROP
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
