CVE-2016-4476 in hostapd
Summary
by MITRE
hostapd 0.6.7 through 2.5 and wpa_supplicant 0.6.7 through 2.5 do not reject \n and \r characters in passphrase parameters, which allows remote attackers to cause a denial of service (daemon outage) via a crafted WPS operation.
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Analysis
by VulDB Data Team • 08/17/2022
The vulnerability identified as CVE-2016-4476 affects hostapd and wpa_supplicant implementations version 0.6.7 through 2.5, representing a critical denial of service weakness that stems from improper input validation during wireless network authentication processes. This flaw specifically targets the handling of passphrase parameters within WPS (Wi-Fi Protected Setup) operations, where the software fails to adequately sanitize input containing carriage return and line feed characters. The vulnerability operates at the application layer within wireless access point and client authentication frameworks, directly impacting the stability and availability of wireless networks that rely on these components for security management.
The technical root cause of this vulnerability lies in the insufficient validation of user-supplied input parameters during WPS configuration processes. When malicious actors submit passphrases containing the characters and, the affected software components fail to properly reject these inputs, allowing them to be processed within the authentication pipeline. This processing failure results in malformed data being handled by the wireless daemon processes, which ultimately leads to daemon crashes and subsequent service outages. The vulnerability specifically relates to CWE-20, "Improper Input Validation," which is a fundamental weakness in software design where input data is not properly checked for validity before being processed, creating opportunities for attackers to manipulate system behavior through crafted inputs.
The operational impact of this vulnerability extends beyond simple service disruption, as it provides attackers with a reliable method to perform denial of service attacks against wireless networks without requiring sophisticated privileges or complex exploitation techniques. Network administrators and security professionals must understand that this vulnerability can be exploited remotely, meaning that adversaries do not need physical access to the wireless infrastructure to cause service interruptions. The affected systems include enterprise wireless networks, public hotspots, and any infrastructure utilizing the vulnerable versions of hostapd or wpa_supplicant, potentially affecting thousands of devices and networks globally. This vulnerability particularly impacts environments where wireless access points are configured to use WPS functionality, as the attack vector specifically targets the WPS operational parameters.
Mitigation strategies for CVE-2016-4476 require immediate software updates to versions that properly validate passphrase inputs and reject problematic characters. Organizations should disable WPS functionality on affected devices when updates are not immediately available, as this removes the attack surface entirely. Network monitoring should be implemented to detect unusual authentication patterns that might indicate exploitation attempts, while regular security assessments should verify that all wireless infrastructure components are running patched versions. The vulnerability also highlights the importance of following security best practices such as implementing proper input sanitization and validation at all levels of network infrastructure software. From an ATT&CK framework perspective, this vulnerability maps to the T1499.004 technique related to network denial of service, where adversaries leverage software weaknesses to disrupt network availability. Additionally, the vulnerability demonstrates the importance of defensive techniques such as input validation and access control measures that can prevent exploitation of similar weaknesses in wireless network infrastructure components.