CVE-2019-5108 in Linux
Summary
by MITRE
An exploitable denial-of-service vulnerability exists in the Linux kernel prior to mainline 5.3. An attacker could exploit this vulnerability by triggering AP to send IAPP location updates for stations before the required authentication process has completed. This could lead to different denial-of-service scenarios, either by causing CAM table attacks, or by leading to traffic flapping if faking already existing clients in other nearby APs of the same wireless infrastructure. An attacker can forge Authentication and Association Request packets to trigger this vulnerability.
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Analysis
by VulDB Data Team • 10/15/2024
The vulnerability described in CVE-2019-5108 represents a critical denial-of-service flaw within the Linux kernel's wireless subsystem, specifically affecting versions prior to mainline 5.3. This weakness resides in the handling of IAPP (Inter-Access Point Protocol) location updates within wireless access point implementations, creating a fundamental security gap that can be exploited by malicious actors to disrupt wireless network operations. The vulnerability stems from insufficient validation of client authentication states before processing location update requests, allowing attackers to manipulate the wireless infrastructure in ways that compromise network stability and availability.
The technical flaw manifests when wireless access points process IAPP location updates for stations that have not yet completed the required authentication and association phases. This condition creates a race window where the system attempts to maintain connection state information for clients that are technically not yet authenticated, leading to inconsistent state management within the kernel's wireless subsystem. The vulnerability specifically affects the CAM (Content Addressable Memory) table management within wireless access points, where entries are created or updated without proper validation of client authentication status. This flaw is categorized under CWE-362, which addresses concurrent execution using shared data structures without proper synchronization, and can be mapped to ATT&CK technique T1499.001 for network disruption attacks.
Attackers can exploit this vulnerability by crafting and transmitting forged Authentication and Association Request packets to the target wireless infrastructure. These packets are designed to trigger the vulnerable code path where IAPP location updates are processed for clients in pre-authentication states. The exploitation can result in two primary denial-of-service scenarios that significantly impact network operations and user experience. The first scenario involves CAM table attacks where the system's connection tracking tables become corrupted or overwhelmed with invalid entries, causing legitimate clients to lose connectivity or forcing the access point to reset its wireless state. The second scenario creates traffic flapping conditions where the wireless infrastructure experiences constant switching between different client states, leading to network instability and potential complete service disruption.
The operational impact of this vulnerability extends beyond simple service interruption to encompass broader network reliability issues that can affect enterprise and infrastructure wireless deployments. When exploited, the vulnerability can cause cascading failures within wireless networks where multiple access points become unstable simultaneously, particularly in environments with overlapping wireless infrastructure where faking existing clients from neighboring APs becomes feasible. Network administrators may observe increased authentication failures, client disconnections, and overall degradation of wireless service quality. The vulnerability affects both enterprise and consumer wireless infrastructure, making it particularly dangerous in environments where wireless networks provide critical connectivity services, such as in healthcare facilities, educational institutions, or industrial control systems where network availability is paramount for operational continuity.
Mitigation strategies for CVE-2019-5108 require immediate kernel updates to versions 5.3 or later where the vulnerability has been addressed through proper authentication state validation in the wireless subsystem. Network administrators should implement robust monitoring solutions to detect anomalous IAPP traffic patterns and authentication request sequences that may indicate exploitation attempts. Additional defensive measures include implementing network segmentation to isolate wireless infrastructure from critical systems, deploying intrusion detection systems specifically configured to monitor wireless protocol anomalies, and establishing baseline network behavior monitoring to quickly identify deviations from normal operation. Organizations should also consider implementing wireless access point hardening procedures that include disabling unnecessary wireless protocols and implementing proper access control lists to limit the scope of potential exploitation. The fix addresses the root cause by ensuring that IAPP location update processing only occurs for authenticated and properly associated clients, thereby preventing the race condition that enables the denial-of-service scenarios.