Remote Stack-Based Buffer Overflow in Tenda W20E

A critical stack-based buffer overflow vulnerability (CVE-2026-19824) has been identified in Tenda W20E routers running firmware version 15.11.0.6(1068_1546_841)_CN_TDC. The flaw resides in the ipMacBindListStore function within the /goform/addIpMacBind endpoint. By sending a crafted IPMacBindRule argument to this endpoint, a remote, authenticated attacker can trigger a buffer overflow, potentially leading to arbitrary code execution on the affected device. Public exploit code is currently available, increasing the risk of exploitation by opportunistic actors. Given the nature of these edge network devices, successful exploitation provides an attacker with a persistent foothold in the internal network environment.

Attack Chain

1. Attacker performs reconnaissance to identify Tenda W20E devices exposed to the internet.
2. Attacker obtains authenticated access to the device management interface (PR:L).
3. Attacker crafts a malicious HTTP POST request targeting the /goform/addIpMacBind endpoint.
4. The request includes an oversized or malformed IPMacBindRule argument designed to exceed the allocated stack buffer.
5. The ipMacBindListStore function processes the malicious argument without sufficient bounds checking.
6. The stack-based buffer overflow occurs, overwriting adjacent memory space.
7. Attacker redirects the instruction pointer to injected shellcode to achieve arbitrary code execution.
8. Final objective is achieved, such as establishing persistent C2 or pivot access into the internal network.

Impact

Successful exploitation of CVE-2026-19824 allows for remote code execution with the privileges of the web management service. This can lead to full device compromise, allowing the attacker to intercept traffic, conduct man-in-the-middle attacks, or use the router as a pivot point to attack other internal systems. As Tenda W20E devices are often deployed in small-to-medium enterprise environments, the potential for lateral movement and broad data access is high.

Recommendation

• Identify and isolate all vulnerable Tenda W20E devices running firmware version 15.11.0.6(1068_1546_841)_CN_TDC from the public internet.
• Disable remote management access on the WAN interface immediately to mitigate the reachability of the /goform/addIpMacBind endpoint.
• Deploy the provided webserver detection rule to monitor for exploitation attempts against the affected URI.
• Check official Tenda support channels for firmware updates that address the vulnerability and apply them as soon as they become available.