CVE-2020-27301 in RTL8710
Summary
by MITRE • 06/04/2021
A stack buffer overflow in Realtek RTL8710 (and other Ameba-based devices) can lead to remote code execution via the "AES_UnWRAP" function, when an attacker in Wi-Fi range sends a crafted "Encrypted GTK" value as part of the WPA2 4-way-handshake.
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Analysis
by VulDB Data Team • 06/07/2021
The vulnerability CVE-2020-27301 represents a critical stack buffer overflow affecting Realtek RTL8710 and other Ameba-based wireless devices that implement the WPA2 authentication protocol. This flaw exists within the AES_UnWRAP function which processes encrypted group temporal keys during the WPA2 4-way handshake process. The vulnerability is particularly concerning because it enables remote code execution without requiring authentication or physical access to the target device, making it exploitable by attackers within Wi-Fi range. The attack vector specifically targets the handling of crafted encrypted GTK values, which are transmitted as part of the standard WPA2 authentication process and are designed to establish secure group communication keys among multiple devices connected to the same wireless network. The buffer overflow occurs when the device fails to properly validate the length of the incoming encrypted GTK data before processing it through the AES_UnWRAP function, creating a condition where attacker-controlled data can overwrite adjacent stack memory regions.
The technical implementation of this vulnerability stems from inadequate input validation within the cryptographic processing routines of the wireless chipset firmware. When a malicious actor sends a specially crafted encrypted GTK frame, the device's firmware does not perform proper bounds checking on the data length before copying it into a fixed-size stack buffer. This allows the attacker to overflow the buffer and potentially overwrite the return address or other critical stack variables, enabling arbitrary code execution with the privileges of the wireless firmware process. The vulnerability is classified under CWE-121 as a stack-based buffer overflow, which directly maps to the attack pattern described in the MITRE ATT&CK framework under technique T1059.007 for command and script injection. The affected devices operate in a privileged execution context where the wireless firmware has direct access to hardware resources, making successful exploitation particularly dangerous as it could allow attackers to gain full control over the device's wireless capabilities and potentially use it as a pivot point for attacking other networked devices.
The operational impact of this vulnerability extends beyond individual device compromise to potentially enable large-scale network infiltration attacks. An attacker within Wi-Fi range can exploit this vulnerability to gain unauthorized access to IoT devices, wireless sensors, smart home appliances, and other networked equipment that rely on Realtek RTL8710 or Ameba-based chipsets. This represents a significant threat to enterprise wireless networks where such devices are commonly deployed, as it allows for lateral movement and persistent access to network resources. The vulnerability affects a wide range of devices including wireless routers, access points, IoT sensors, and embedded systems that implement the WPA2 protocol. The remote nature of the attack means that traditional network segmentation measures may not prevent exploitation, and the lack of authentication requirements makes detection particularly challenging. Organizations should consider this vulnerability as a potential entry point for advanced persistent threats and evaluate their wireless infrastructure for affected devices, as the exploitation can occur without any user interaction or device-specific credentials.
Mitigation strategies for CVE-2020-27301 should focus on both immediate remediation and long-term network security improvements. The primary recommendation is to apply firmware updates from device manufacturers that address the buffer overflow in the AES_UnWRAP function, though many affected devices may no longer receive security updates due to their embedded nature. Network administrators should implement additional security controls such as disabling WPA2 4-way handshake processing on vulnerable devices when possible, or implementing network segmentation to isolate affected devices from critical network resources. Monitoring network traffic for suspicious encrypted GTK frames and implementing intrusion detection systems that can identify malformed WPA2 handshake messages represents an important defensive measure. The vulnerability highlights the importance of secure coding practices in embedded wireless firmware and reinforces the need for comprehensive security testing of cryptographic implementations in IoT devices. Organizations should also consider migrating to more secure wireless protocols such as WPA3 where available, and regularly audit their wireless infrastructure for devices that may be running outdated firmware versions that could be susceptible to similar vulnerabilities. This vulnerability serves as a reminder of the critical security risks associated with embedded wireless chipsets and the importance of maintaining up-to-date firmware in wireless network infrastructure.