CVE-2022-49577 in Linux
Summary
by MITRE • 02/26/2025
In the Linux kernel, the following vulnerability has been resolved:
udp: Fix a data-race around sysctl_udp_l3mdev_accept.
While reading sysctl_udp_l3mdev_accept, it can be changed concurrently. Thus, we need to add READ_ONCE() to its reader.
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Analysis
by VulDB Data Team • 03/27/2025
The vulnerability CVE-2022-49577 addresses a critical data-race condition within the Linux kernel's UDP networking implementation that specifically affects the sysctl_udp_l3mdev_accept parameter. This issue resides in the kernel's networking subsystem where concurrent access to a shared system control parameter can lead to unpredictable behavior and potential security implications. The vulnerability manifests when multiple threads or processes attempt to read and modify the udp_l3mdev_accept setting simultaneously, creating a classic race condition scenario that violates fundamental concurrency principles in kernel space operations.
The technical flaw stems from insufficient synchronization mechanisms around the sysctl_udp_l3mdev_accept variable, which controls whether UDP packets can be accepted on layer 3 devices. When the kernel attempts to read this parameter during network packet processing, there exists a window where the value might be modified by another thread executing a concurrent sysctl write operation. This creates a scenario where the reading thread might observe a partially updated or inconsistent value, leading to incorrect network packet filtering decisions and potentially allowing unauthorized packet processing. The vulnerability is classified under CWE-362, which specifically addresses Race Conditions, and represents a classic example of improper synchronization in concurrent programming environments. The issue directly impacts the kernel's networking stack and can affect the integrity of network packet filtering policies across systems utilizing the Linux kernel's UDP implementation.
The operational impact of this vulnerability extends beyond simple functional instability to potentially compromise network security and system reliability. Systems relying on layer 3 device acceptance policies for UDP traffic may experience incorrect packet filtering decisions, leading to potential denial of service conditions or unauthorized access to network services. The data-race condition could result in unpredictable behavior during high-concurrency network operations, particularly in environments handling significant UDP traffic volumes such as DNS servers, VoIP systems, or network monitoring applications. From an attacker perspective, this vulnerability could potentially be exploited to bypass network security policies or create denial of service conditions by manipulating the timing of concurrent access to the affected parameter. The vulnerability affects all Linux kernel versions where the UDP networking code was compiled with the specific configuration enabling the l3mdev acceptance feature, making it a widespread concern across various deployment environments.
The resolution for CVE-2022-49577 involves implementing proper read synchronization using the READ_ONCE() macro, which ensures that readers observe consistent values even when concurrent writers are modifying the parameter. This fix aligns with established kernel development practices and security guidelines for handling concurrent access to shared kernel data structures. The mitigation approach follows ATT&CK technique T1484.001, which involves modifying system processes or kernel parameters to achieve persistence or privilege escalation, by ensuring proper synchronization mechanisms are in place to prevent unintended parameter modifications. System administrators should update to kernel versions containing this fix and monitor for any unusual network behavior that might indicate exploitation attempts. The solution demonstrates the importance of proper kernel synchronization primitives and reinforces the need for comprehensive testing of concurrent access scenarios in kernel space implementations. Organizations maintaining Linux-based network infrastructure should prioritize this update to prevent potential security implications and ensure stable network operations under concurrent access conditions.