CVE-2020-15023 in AP5100W
Summary
by MITRE • 12/11/2020
Askey AP5100W devices through AP5100W_Dual_SIG_1.01.097 are affected by WPS PIN offline brute-force cracking. This arises because of issues with the random number selection for the Diffie-Hellman exchange. By capturing an attempted (and even failed) WPS authentication attempt, it is possible to brute force the overall authentication exchange. This allows an attacker to obtain the recovered WPS PIN in minutes or even seconds, and eventually obtain the Wi-Fi PSK key, gaining access to the Wi=Fi network.
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Analysis
by VulDB Data Team • 12/16/2020
The CVE-2020-15023 vulnerability affects Askey AP5100W wireless access points running firmware versions up to AP5100W_Dual_SIG_1.01.097, presenting a critical security flaw in the Wi-Fi Protected Setup implementation. This vulnerability specifically targets the WPS PIN brute-force resistance mechanisms, exploiting weaknesses in the cryptographic random number generation process. The flaw stems from inadequate entropy in the Diffie-Hellman key exchange implementation, which is a fundamental component of the WPS protocol's security architecture. According to CWE-330, this represents a weakness in random number generation where insufficient entropy leads to predictable cryptographic values that can be exploited by attackers.
The technical exploitation of this vulnerability occurs through the capture and analysis of WPS authentication attempts, whether successful or failed, which are transmitted in the WPS protocol's M2 and M4 messages. These messages contain the necessary information to perform offline brute-force attacks against the WPS PIN, which is typically a 8-digit numeric code. The weakness in the random number selection process for Diffie-Hellman exchanges means that the mathematical relationships between the transmitted values can be reverse-engineered to significantly reduce the search space for the PIN. This vulnerability directly relates to ATT&CK technique T1115 where adversaries exploit weaknesses in authentication protocols to gain unauthorized access.
The operational impact of this vulnerability is severe as it allows an attacker to recover the WPS PIN within minutes or even seconds, typically requiring only a single captured authentication attempt. Once the WPS PIN is obtained, the attacker can derive the corresponding Wi-Fi Pre-Shared Key (PSK), thereby gaining complete access to the wireless network. This compromises the network's confidentiality, integrity, and availability, as unauthorized users can eavesdrop on communications, modify network traffic, or launch further attacks against connected devices. The vulnerability affects networks where WPS is enabled, making it particularly dangerous in environments where administrators may not be aware of the risks associated with WPS functionality.
Mitigation strategies for CVE-2020-15023 should focus on disabling WPS functionality entirely on affected devices, as this removes the attack surface entirely. Network administrators should also implement proper firmware updates from the vendor when available, though in this case the vulnerability affects multiple firmware versions requiring immediate action. Additional defensive measures include monitoring for unauthorized WPS authentication attempts, implementing network segmentation to limit the impact of potential breaches, and employing robust wireless network monitoring tools to detect anomalous authentication patterns. The vulnerability highlights the importance of proper cryptographic implementation and the necessity of avoiding predictable random number generation in security-critical protocols, aligning with security best practices outlined in NIST SP 800-90A regarding cryptographic random number generation requirements.