CVE-2026-2871 is a stack-based buffer overflow vulnerability identified in the Tenda A21 router firmware version 1.0.0.0. The vulnerability resides in the fromSetIpMacBind function, which is accessible via the /goform/SetIpMacBind endpoint. This function improperly handles input arguments, allowing an attacker to craft a malicious request that overflows a stack buffer. This overflow can corrupt the stack, potentially enabling remote code execution or denial of service without requiring authentication or user interaction. The vulnerability is remotely exploitable over the network, making it particularly dangerous for exposed devices. The CVSS 4.0 score of 8.7 reflects the high impact on confidentiality, integrity, and availability, combined with low attack complexity and no privileges or user interaction needed. Although no patches have been linked yet, the public availability of an exploit increases the urgency for mitigation. The flaw could be leveraged by attackers to gain control over the device, intercept or manipulate network traffic, or disrupt network services. Given the critical role of routers in network infrastructure, exploitation could have cascading effects on organizational security.

The impact of CVE-2026-2871 is significant for organizations using Tenda A21 routers, as successful exploitation can lead to full compromise of the device. Attackers could execute arbitrary code remotely, potentially gaining control over the router’s firmware and configuration. This can result in interception or manipulation of network traffic, unauthorized access to internal networks, and disruption of network availability. The vulnerability threatens confidentiality by exposing sensitive network data, integrity by allowing unauthorized configuration changes, and availability by enabling denial-of-service conditions. Organizations relying on these routers for critical network functions face risks of lateral movement by attackers and persistent footholds within their infrastructure. The public availability of exploits increases the likelihood of widespread attacks, especially targeting unpatched devices. This can affect both enterprise and consumer environments, with potential impacts on business continuity and data security.

1. Immediate mitigation should focus on isolating affected Tenda A21 devices from untrusted networks, especially the internet, to reduce exposure. 2. Monitor network traffic for unusual requests targeting /goform/SetIpMacBind and implement firewall rules to block suspicious or malformed requests to this endpoint. 3. If possible, disable or restrict access to the IP-MAC binding feature or the vulnerable endpoint until a vendor patch is available. 4. Regularly check for firmware updates from Tenda and apply patches promptly once released. 5. Employ network segmentation to limit the impact of compromised devices and restrict administrative access to trusted hosts only. 6. Use intrusion detection/prevention systems (IDS/IPS) with signatures for this exploit to detect and block attempts. 7. Conduct thorough audits of router configurations and logs to identify any signs of exploitation or unauthorized changes. 8. Educate network administrators about this vulnerability and ensure incident response plans include steps for router compromise scenarios.