CVE-2026-28520 is an off-by-one error resulting in a single-byte buffer overflow within the WiFiMulti component of the arduino-TuyaOpen library, versions prior to 1.2.1. This library is commonly integrated into Tuya-based embedded IoT devices to manage WiFi connectivity. The vulnerability manifests when a device attempts to connect to a WiFi access point controlled by an attacker. Due to improper bounds checking, the attacker can overflow a buffer by one byte, enabling arbitrary code execution on the embedded device. This can lead to full compromise of the device’s firmware, allowing attackers to manipulate device behavior, exfiltrate data, or pivot within a network. The vulnerability requires no authentication or user interaction, as exploitation occurs during automatic WiFi connection attempts. The CVSS 4.0 vector (AV:L/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N) indicates local attack vector (local network), low attack complexity, no privileges or user interaction needed, and high impact on confidentiality, integrity, and availability. Although no public exploits are reported yet, the vulnerability poses a significant threat to the security of IoT ecosystems relying on Tuya’s arduino-TuyaOpen library. The lack of segmentation or sandboxing on many embedded devices exacerbates the risk of full device compromise.

The vulnerability allows attackers to execute arbitrary code on embedded IoT devices, potentially leading to full device takeover. This can result in unauthorized control over smart home or industrial IoT devices, data theft, disruption of device functionality, or use of compromised devices as footholds for lateral movement within enterprise or home networks. Given the widespread use of Tuya-based devices in consumer, commercial, and industrial environments, the impact is broad. Critical infrastructure relying on such devices could face operational disruptions. The ability to exploit the vulnerability without authentication or user interaction increases the risk of automated or large-scale attacks, especially in environments where devices connect to multiple WiFi networks or untrusted hotspots. The compromise of device confidentiality, integrity, and availability could undermine trust in IoT deployments and lead to significant financial and reputational damage for organizations.

1. Upgrade all affected devices to arduino-TuyaOpen version 1.2.1 or later, where the buffer overflow has been fixed. 2. Implement strict network access controls to prevent devices from connecting to untrusted or attacker-controlled WiFi access points. This includes configuring devices to connect only to known, secure networks and disabling automatic connections to open or unknown hotspots. 3. Employ network segmentation to isolate IoT devices from critical infrastructure and sensitive data networks, limiting the impact of any compromise. 4. Monitor network traffic for unusual WiFi connection attempts or rogue access points, using wireless intrusion detection systems (WIDS). 5. For organizations deploying Tuya-based devices at scale, conduct regular firmware audits and vulnerability assessments to ensure devices are up to date. 6. Consider deploying endpoint detection and response (EDR) solutions tailored for IoT devices where feasible to detect anomalous behavior post-exploitation. 7. Educate users and administrators about the risks of connecting IoT devices to untrusted networks and enforce policies to minimize exposure.