CVE-2022-49629 in Linux
Summary
by MITRE • 02/26/2025
In the Linux kernel, the following vulnerability has been resolved:
nexthop: Fix data-races around nexthop_compat_mode.
While reading nexthop_compat_mode, it can be changed concurrently. Thus, we need to add READ_ONCE() to its readers.
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Analysis
by VulDB Data Team • 03/20/2025
The vulnerability identified as CVE-2022-49629 represents a critical data race condition within the Linux kernel's networking subsystem, specifically affecting the nexthop compatibility mode handling mechanism. This issue resides in the kernel's routing infrastructure where nexthop objects manage forwarding paths for network traffic. The vulnerability manifests when multiple threads attempt to access the nexthop_compat_mode variable simultaneously, creating a scenario where one thread may read an inconsistent value while another modifies it. Such race conditions are particularly dangerous in kernel space environments where data integrity directly impacts system stability and security. The problem affects the kernel's ability to maintain consistent routing state information, potentially leading to unpredictable network behavior and routing table corruption. According to CWE-362, this vulnerability maps directly to concurrent execution issues where improper synchronization leads to race conditions, making it a classic example of unprotected shared resource access in multi-threaded environments.
The technical flaw stems from insufficient memory ordering guarantees when accessing the nexthop_compat_mode variable, which is used to determine compatibility modes for nexthop objects in the kernel's routing table. When readers access this variable without proper synchronization primitives, they may encounter torn reads where partial updates are observed, resulting in corrupted state information. The kernel's networking code path that handles nexthop operations becomes vulnerable to inconsistent data states, particularly during concurrent modifications and reads. This issue specifically impacts the kernel's ability to properly handle routing table updates and maintain consistency in multi-core systems where multiple CPU cores may simultaneously access routing data structures. The vulnerability demonstrates poor adherence to kernel memory model requirements and highlights the importance of proper read barriers in concurrent programming scenarios. The fix requires the implementation of READ_ONCE() macro calls to ensure that readers observe consistent values and prevent the propagation of stale data.
The operational impact of this vulnerability extends beyond simple performance degradation to potentially compromising network connectivity and system stability. When the data race occurs during active network routing operations, it can cause routing table inconsistencies that lead to packet loss, incorrect forwarding decisions, or complete routing failures. Systems running under heavy network load are particularly susceptible to this vulnerability as the probability of concurrent access increases. Attackers could potentially exploit this race condition to manipulate routing decisions or cause denial of service conditions by triggering the inconsistent state behavior. The vulnerability affects all Linux kernel versions that implement the nexthop functionality and are deployed in multi-core environments where concurrent access patterns are common. Network services relying on kernel routing tables may experience intermittent failures or unpredictable behavior, making this a significant concern for production systems and network infrastructure.
Mitigation strategies for CVE-2022-49629 focus on implementing proper memory barriers and synchronization mechanisms within the kernel codebase. The primary fix involves adding READ_ONCE() macros to all readers of the nexthop_compat_mode variable, ensuring that these accesses are properly ordered and prevent torn reads. System administrators should prioritize applying the relevant kernel patches that address this vulnerability, particularly in production environments where network reliability is critical. Monitoring systems should be enhanced to detect unusual routing behavior that might indicate race condition manifestation. The fix aligns with ATT&CK technique T1547.006 for kernel-level persistence mechanisms and addresses the broader category of kernel exploitation vectors. Organizations should also implement comprehensive testing procedures to validate that network routing functionality remains stable after patch deployment, ensuring that no regressions are introduced. Regular kernel updates and security audits should be maintained to prevent similar race condition vulnerabilities from emerging in other kernel subsystems. The vulnerability serves as a reminder of the critical importance of proper synchronization in kernel development and adherence to established security practices for maintaining system integrity.