CVE-2020-25855 in RTL8195A
Summary
by MITRE • 02/03/2021
The function AES_UnWRAP() in the Realtek RTL8195A Wi-Fi Module prior to versions released in April 2020 (up to and excluding 2.08) does not validate the size parameter for a memcpy() operation, resulting in a stack buffer overflow which can be exploited for remote code execution or denial of service. An attacker can impersonate an Access Point and attack a vulnerable Wi-Fi client, by injecting a crafted packet into the WPA2 handshake. The attacker needs to know the network's PSK in order to exploit this.
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 01/27/2023
The CVE-2020-25855 vulnerability resides within the Realtek RTL8195A Wi-Fi module firmware, specifically in the AES_UnWRAP() function that handles cryptographic operations during WPA2 authentication processes. This flaw represents a critical stack buffer overflow condition that arises from inadequate input validation during memory operations. The vulnerability affects firmware versions prior to those released in April 2020, encompassing all versions up to but not including 2.08, making it a widespread issue across numerous embedded Wi-Fi devices that rely on this chipset. The technical implementation flaw manifests when the function processes a memcpy() operation without validating the size parameter, creating an exploitable condition where attacker-controlled data can overwrite adjacent stack memory regions.
The operational impact of this vulnerability extends beyond simple denial of service to encompass full remote code execution capabilities within the affected device's operational environment. An attacker must first obtain the network's pre-shared key to successfully exploit this vulnerability, which limits the attack surface but does not eliminate the serious security implications. The attack vector requires the adversary to impersonate a legitimate access point and inject malicious packets into the WPA2 handshake process, leveraging the cryptographic weaknesses in the RTL8195A's implementation. This approach aligns with common wireless attack methodologies documented in the MITRE ATT&CK framework under the wireless network attack techniques, specifically targeting the authentication and key exchange phases of wireless communications.
The underlying technical flaw directly maps to CWE-121, which describes stack-based buffer overflow conditions, and CWE-122, which addresses heap-based buffer overflow scenarios. These classifications highlight the fundamental memory corruption vulnerability that allows attackers to manipulate program execution flow through controlled data injection into memory regions. The specific implementation error occurs during the WPA2 handshake process where the AES_UnWRAP() function processes key derivation material without proper boundary checking, creating a predictable overflow condition that can be leveraged for arbitrary code execution. The vulnerability's exploitation requires precise packet crafting and timing, making it more sophisticated than typical buffer overflow attacks but still within the realm of feasible exploitation by determined adversaries.
Device manufacturers and system administrators should prioritize firmware updates to address this vulnerability, as the affected RTL8195A chipset powers numerous IoT devices, routers, and embedded systems. The mitigation strategy involves implementing proper input validation for all memory operations, particularly memcpy() calls that process user-supplied data. Additionally, network segmentation and monitoring solutions should be deployed to detect anomalous wireless traffic patterns that might indicate exploitation attempts. The vulnerability demonstrates the critical importance of cryptographic implementation review in embedded systems, particularly those handling wireless security protocols where the attack surface can be exploited remotely. Organizations should also consider implementing network access control measures and monitoring for unauthorized access point impersonation attempts to reduce the risk of exploitation in environments where complete firmware updates may not be immediately available.