CVE-2026-72229 in Linux
Summary
by MITRE • 08/15/2026
In the Linux kernel, the following vulnerability has been resolved:
batman-adv: clean untagged VLAN on netdev registration failure
When an mesh interface is registered, it creates an untagged struct batadv_meshif_vlan on top of it via the NETDEV_REGISTER notifier. But in this process, another receiver of this notification can veto the registration. The netdev registration will be aborted because of this veto.
The register_netdevice() call will try to clean up the net_device using unregister_netdevice_queue() - which only uses the .priv_destructor to free private resources. In this situation, .dellink will not be called.
The cleanup of the untagged batadv_meshif_vlan must thefore be done in the destructor to avoid a leak of this object.
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Analysis
by VulDB Data Team • 08/15/2026
This vulnerability exists within the batman-adv kernel module, which implements the B.A.T.M.A.N. ad-hoc mesh routing protocol for linux networks. The issue stems from improper resource management during network device registration processes where memory leaks can occur due to incomplete cleanup operations. When a mesh interface is registered, the system creates an untagged struct batadv_meshif_vlan structure to manage the interface's virtual local area network configuration. This occurs through the NETDEV_REGISTER notifier mechanism that allows multiple subsystems to receive notifications about network device registration events.
The flaw manifests when another component registered to receive the NETDEV_REGISTER notification chooses to veto the registration process. In such cases, the netdev registration is aborted but the cleanup process becomes incomplete. The register_netdevice() function attempts to clean up the net_device using unregister_netdevice_queue() which only invokes the .priv_destructor callback for freeing private resources but does not call the .dellink callback that would normally handle the proper removal of mesh interface VLAN structures. This architectural gap creates a memory leak scenario where the untagged batadv_meshif_vlan object remains allocated in memory even though the network device registration has been abandoned.
The operational impact of this vulnerability represents a memory management issue that can lead to progressive resource exhaustion over time, particularly in environments with frequent mesh interface creation and deletion operations. While the immediate security implications may appear limited to resource consumption rather than direct exploitation, such leaks can contribute to system instability and performance degradation. The vulnerability affects systems running linux kernels with batman-adv mesh networking capabilities where dynamic network device management occurs regularly.
Mitigation strategies should focus on implementing proper cleanup logic within the private destructor callback to ensure that untagged VLAN structures are properly freed regardless of whether registration succeeds or fails. This requires modifying the batadv_meshif_vlan cleanup routine to be called from the .priv_destructor path rather than relying solely on the .dellink callback which only executes during successful registration completion. The fix should align with secure coding practices that prevent resource leaks in kernel modules and follow established patterns for proper memory management within network device drivers. This vulnerability type relates to CWE-404, improper resource cleanup, and could be categorized under ATT&CK technique T1547.006 for privilege escalation through kernel module manipulation.
The root cause of this issue demonstrates a fundamental misunderstanding of the notification lifecycle in linux kernel networking subsystems where different callback mechanisms handle different phases of device registration and cleanup. The solution requires careful attention to the distinction between successful registration completion and aborted registration scenarios, ensuring that all allocated resources are properly accounted for in both code paths. Proper implementation should include explicit checks within the destructor function to verify that untagged VLAN structures are cleaned up appropriately during failed registration attempts, preventing any potential for persistent memory leaks that could be exploited over time through resource exhaustion attacks.