Executive brief
The Tenda W20E enterprise router is vulnerable to a security flaw that can be used to crash the device. By sending a specially crafted web request to the router's management interface, an attacker can trigger a system failure, leading to a denial of service. This disrupts internet connectivity and network operations for all connected users until the device is recovered.
Technical details
A stack-based buffer overflow exists in the Tenda W20E router firmware version v15.11.0.6. The vulnerability is located within the 'fromSetDhcpRules' function, specifically inside the 'modifyDhcpRule' sub-function. The 'bindMACAddr' HTTP parameter is retrieved via 'websGetVar' and subsequently passed to 'snprintf' with a fixed-size destination buffer of 0x2f bytes. An attacker can provide an overly long string (e.g., 888 characters) for the 'bindMACAddr' parameter to overflow the buffer. This can be exploited via a network-reachable HTTP request to the 'setDhcpRules' action, resulting in a process crash or device instability (Denial of Service).
Affected products
- Tenda W20E v15.11.0.6
Timeline
- 2026-03-19: other: CVE request submitted to MITRE
- 2026-06-06: disclosed: Public disclosure
- 2026-06-09: advisory: NVD published date