CVE-2022-49920 in Linux
Summary
by MITRE • 05/01/2025
In the Linux kernel, the following vulnerability has been resolved:
netfilter: nf_tables: netlink notifier might race to release objects
commit release path is invoked via call_rcu and it runs lockless to release the objects after rcu grace period. The netlink notifier handler might win race to remove objects that the transaction context is still referencing from the commit release path.
Call rcu_barrier() to ensure pending rcu callbacks run to completion if the list of transactions to be destroyed is not empty.
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Analysis
by VulDB Data Team • 03/15/2026
The vulnerability described in CVE-2022-49920 resides within the Linux kernel's netfilter subsystem, specifically in the nf_tables implementation that handles netlink communication for network filtering rules. This issue represents a race condition that can lead to improper object cleanup and potential system instability. The flaw occurs in the commit release path where objects are scheduled for deletion using the call_rcu mechanism, which operates without traditional locking mechanisms to ensure memory safety during the grace period. The core problem emerges when the netlink notifier handler executes concurrently with the transaction commit process, creating a scenario where objects may be prematurely removed from memory while still being referenced by the ongoing transaction context.
The technical implementation of this vulnerability involves the interaction between the RCU (Read-Copy-Update) subsystem and the netlink notification framework within the kernel's networking stack. When a transaction involving netfilter rules is committed, the system schedules object cleanup through call_rcu which defers actual memory deallocation until after a grace period to ensure no ongoing readers are accessing the objects. However, the netlink notifier handler can potentially execute before this grace period completes and remove objects from the system, while the transaction commit path is still attempting to reference these same objects. This race condition creates a scenario where the transaction context may attempt to access memory that has already been freed, leading to potential kernel crashes, data corruption, or privilege escalation opportunities. The vulnerability is classified under CWE-362 as a race condition in kernel memory management, which directly aligns with the characteristics of concurrent access to shared resources without proper synchronization.
The operational impact of CVE-2022-49920 extends beyond simple system instability to potentially compromise the integrity of the network filtering infrastructure. Attackers could exploit this vulnerability by crafting specific netlink messages that trigger the race condition during rule modifications, potentially causing denial of service through kernel panics or more serious security implications if the race allows for memory corruption that could be leveraged for privilege escalation. The vulnerability affects systems running Linux kernels that implement nf_tables and utilize netlink communication for network rule management, making it particularly concerning for network appliances, firewalls, and systems with active netfilter configurations. From an ATT&CK perspective, this vulnerability could map to privilege escalation techniques through kernel memory corruption, and potentially to defense evasion by disrupting network filtering capabilities that protect against malicious traffic.
Mitigation strategies for this vulnerability require kernel-level patches that address the race condition through proper synchronization mechanisms. The recommended solution involves implementing call_rcu_barrier() to ensure that all pending RCU callbacks complete execution before proceeding with object destruction when transaction lists remain to be processed. This approach ensures proper ordering and prevents premature object removal that could lead to reference violations. System administrators should prioritize applying the kernel patches provided by their distribution vendors, as the vulnerability affects core kernel functionality that is critical for network security operations. Organizations should also implement monitoring for unusual network filtering behavior or kernel panic events that could indicate exploitation attempts, while maintaining up-to-date kernel versions to prevent potential exploitation through this race condition in the netfilter subsystem's object management.