CVE-2019-9496 in hostapd
Summary
by MITRE
An invalid authentication sequence could result in the hostapd process terminating due to missing state validation steps when processing the SAE confirm message when in hostapd/AP mode. All version of hostapd with SAE support are vulnerable. An attacker may force the hostapd process to terminate, performing a denial of service attack. Both hostapd with SAE support and wpa_supplicant with SAE support prior to and including version 2.7 are affected.
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Analysis
by VulDB Data Team • 08/29/2023
The vulnerability described in CVE-2019-9496 represents a critical denial of service weakness within the hostapd wireless access point daemon that specifically affects implementations supporting the Simultaneous Authentication of Equals (SAE) protocol. This protocol, also known as WPA3, was introduced to replace the vulnerable WPA2 PSK authentication mechanism and provides enhanced security through a more robust key exchange process. The flaw manifests when hostapd processes SAE confirm messages in AP mode, where the authentication sequence lacks proper state validation checks that should occur during the protocol negotiation phase.
The technical root cause of this vulnerability stems from inadequate state management within the hostapd implementation when handling SAE confirm messages. During the SAE handshake process, the hostapd daemon must maintain strict state validation to ensure that each message in the authentication sequence is properly received and processed before transitioning to the next phase. When this validation is missing or improperly implemented, an attacker can craft malicious SAE confirm messages that cause the hostapd process to enter an inconsistent state, ultimately leading to process termination. This represents a classic example of improper state handling that falls under CWE-362, which specifically addresses concurrent execution issues such as race conditions and improper state management.
The operational impact of this vulnerability extends beyond simple service disruption, as it provides attackers with a straightforward method to perform denial of service attacks against wireless networks that rely on hostapd for authentication services. Network administrators running vulnerable versions of hostapd with SAE support are at risk of having their wireless access points become unavailable, potentially disrupting network connectivity for all connected devices. The attack vector is particularly concerning because it requires minimal expertise to execute, as attackers only need to send specially crafted SAE confirm messages to trigger the process termination. This vulnerability affects both hostapd and wpa_supplicant implementations, meaning that the attack surface extends to both access point and client devices, creating a comprehensive denial of service scenario.
The implications of this vulnerability align with several ATT&CK framework techniques, particularly those related to service disruption and credential access. The attack pattern fits within the T1499.004 sub-technique for network denial of service, where attackers target wireless infrastructure to prevent legitimate users from accessing network resources. Additionally, since this affects the core authentication process, it could potentially be leveraged as a stepping stone for more sophisticated attacks that might attempt to manipulate the wireless authentication flow, although the primary impact remains focused on service disruption. Organizations should consider this vulnerability as part of a broader security assessment that includes wireless network infrastructure, particularly in environments where wireless access points are critical to business operations.
Mitigation strategies for CVE-2019-9496 require immediate patching of all affected hostapd and wpa_supplicant implementations to versions that properly implement state validation during SAE confirm message processing. Network administrators should prioritize updating their wireless infrastructure, particularly in environments where wireless access points are critical to operations. Additionally, implementing network monitoring solutions that can detect anomalous SAE handshake behavior may provide early warning of potential exploitation attempts. The vulnerability highlights the importance of proper state validation in cryptographic protocol implementations and serves as a reminder that even security-enhancing protocols like SAE require careful implementation to avoid introducing new attack vectors. Organizations should also consider implementing redundant wireless access points or alternative authentication mechanisms as part of their overall network resilience strategy to mitigate the impact of such denial of service attacks.