CVE-2022-49596 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_min_snd_mss.
While reading sysctl_tcp_min_snd_mss, it can be changed concurrently. Thus, we need to add READ_ONCE() to its readers.
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Analysis
by VulDB Data Team • 06/13/2025
The vulnerability identified as CVE-2022-49596 represents a critical data race condition within the Linux kernel's TCP implementation that specifically affects the sysctl_tcp_min_snd_mss parameter. This issue occurs in the kernel's networking subsystem where concurrent access to a shared system control parameter creates potential for inconsistent or corrupted data reads. The problem manifests when multiple threads or processes attempt to read the sysctl_tcp_min_snd_mss value simultaneously while another thread modifies it, leading to unpredictable behavior in TCP socket operations. Such data races are particularly dangerous in kernel space environments where inconsistent state can lead to system instability, security vulnerabilities, or denial of service conditions. The vulnerability resides in the kernel's TCP protocol implementation and directly impacts how minimum send MSS values are handled during network communications.
The technical flaw stems from insufficient synchronization mechanisms when accessing the sysctl_tcp_min_snd_mss parameter in the Linux kernel's TCP stack. This parameter controls the minimum segment size that can be sent over TCP connections, which is critical for network performance optimization and proper packet handling. When multiple kernel threads attempt to read this value concurrently with modifications, the absence of proper memory barriers or atomic read operations results in potential race conditions where readers might obtain partially updated values or inconsistent data states. The kernel's networking code lacks the necessary READ_ONCE() macro usage to ensure safe concurrent access to this shared parameter, creating a scenario where the data integrity is compromised during simultaneous read and write operations. This type of race condition falls under the category of memory consistency issues commonly classified as CWE-362 in the Common Weakness Enumeration catalog, representing a concurrent execution condition where a race occurs during data access.
The operational impact of this vulnerability extends across various Linux kernel versions and affects systems heavily reliant on TCP networking operations, particularly those involving high-concurrency network processing or real-time communication scenarios. Systems experiencing heavy network traffic or those implementing complex network policies may be more susceptible to the race condition manifesting as corrupted TCP segment handling, connection instability, or unexpected network behavior. The vulnerability could potentially be exploited by malicious actors to cause system instability through carefully crafted network traffic patterns that trigger the race condition, though direct exploitation for privilege escalation or remote code execution appears limited. However, the indirect impact on system reliability and network service availability makes this vulnerability particularly concerning for production environments where network stability is critical. The issue demonstrates how seemingly simple parameter access operations in kernel space can create complex concurrency problems that affect fundamental network protocols.
Mitigation strategies for CVE-2022-49596 involve applying the appropriate kernel security patches that introduce proper READ_ONCE() usage for the sysctl_tcp_min_snd_mss parameter access. System administrators should prioritize updating their kernel versions to include the fix provided by the Linux kernel maintainers, which typically involves modifications to the TCP implementation code to ensure atomic access patterns for the affected parameter. The fix addresses the core issue by implementing proper memory access semantics that prevent concurrent read-modify-write operations from causing data corruption. Organizations should also consider implementing monitoring solutions to detect unusual network behavior that might indicate race condition exploitation attempts. Additionally, system hardening practices such as restricting unnecessary network access and implementing proper network segmentation can reduce the attack surface while the kernel patches are being deployed. This vulnerability aligns with ATT&CK technique T1059.003 for kernel-level attacks and demonstrates the importance of proper synchronization in kernel programming, particularly in the context of the Linux kernel's networking subsystem where concurrency issues can have widespread impact across network operations and system stability.