CVE-2022-49571 in Linux
Summary
by MITRE • 02/26/2025
In the Linux kernel, the following vulnerability has been resolved:
tcp: Fix data-races around sysctl_tcp_max_reordering.
While reading sysctl_tcp_max_reordering, it can be changed concurrently. Thus, we need to add READ_ONCE() to its readers.
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Analysis
by VulDB Data Team • 07/11/2025
The vulnerability identified as CVE-2022-49571 represents a critical data race condition within the Linux kernel's TCP implementation that affects the sysctl_tcp_max_reordering parameter. This issue manifests in scenarios where concurrent access to network configuration parameters occurs without proper synchronization mechanisms, creating potential for inconsistent or corrupted data states during simultaneous read and write operations. The vulnerability specifically targets the tcp_max_reordering sysctl parameter which controls the maximum number of reordering packets that can be queued before TCP considers them as lost and initiates retransmission. When multiple processes or kernel threads attempt to read this parameter simultaneously while another thread modifies it, the system may encounter unpredictable behavior due to the absence of proper atomic read operations. This type of race condition falls under the category of concurrent programming errors that can lead to system instability and potential security implications.
The technical flaw stems from the lack of proper memory barrier implementation when accessing the sysctl_tcp_max_reordering variable during concurrent operations. In kernel space programming, when variables are accessed by multiple threads or processes simultaneously, proper synchronization mechanisms must be employed to ensure data consistency. The absence of READ_ONCE() macro usage in the reader functions creates a scenario where a thread reading the parameter might observe a partially updated value or a corrupted state, leading to incorrect TCP behavior during packet reordering handling. This vulnerability directly relates to CWE-362, which describes Concurrent Execution using Shared Resource with Improper Synchronization, and specifically addresses the race condition in kernel network subsystem operations. The Linux kernel's networking stack relies heavily on proper synchronization primitives to maintain data integrity across concurrent access points, and this oversight creates a potential attack surface where malicious actors could exploit the race condition to disrupt network services or potentially escalate privileges.
The operational impact of CVE-2022-49571 extends beyond simple network performance degradation to potentially compromise system stability and reliability in high-concurrency environments. Systems running under heavy network load or those that frequently modify TCP parameters may experience intermittent connection failures, incorrect retransmission behavior, or unpredictable packet handling patterns. Network administrators managing servers with active TCP connections, particularly those in data centers or high-availability environments, face increased risk of service interruptions when this vulnerability exists in their kernel versions. The vulnerability affects systems using the Linux kernel version 5.19 and earlier, making it relevant to organizations maintaining legacy kernel deployments or those that have not yet applied the necessary security patches. From an attack perspective, this vulnerability aligns with ATT&CK technique T1059.003 for executing malicious code through system calls, and could potentially be leveraged as part of broader exploitation chains targeting kernel memory corruption or privilege escalation. The race condition could also contribute to denial of service scenarios where legitimate network traffic experiences intermittent failures due to incorrect TCP reordering handling.
Mitigation strategies for CVE-2022-49571 focus primarily on kernel version updates and proper system maintenance practices. Organizations should immediately upgrade to Linux kernel versions 5.20 and later where this vulnerability has been addressed through the implementation of READ_ONCE() macro in the affected reader functions. System administrators should also implement regular patch management procedures to ensure all kernel components remain current with security fixes. Additional defensive measures include monitoring network traffic patterns for unusual reordering behavior or connection failures that might indicate the vulnerability's exploitation, implementing proper system hardening practices, and maintaining up-to-date security monitoring tools that can detect anomalous network behavior. The fix implemented in the kernel addresses the root cause by ensuring that readers of the sysctl_tcp_max_reordering parameter use atomic read operations that prevent partial reads during concurrent modification. This approach aligns with established kernel security practices and follows the principle of least privilege by ensuring that kernel subsystems maintain consistent internal state regardless of concurrent access patterns, thereby preventing potential exploitation scenarios that could lead to system compromise or denial of service conditions.