CVE-2026-68301 in Linux
Summary
by MITRE • 08/10/2026
In the Linux kernel, the following vulnerability has been resolved:
net: hsr: fix memory leak on slave unregistration by removing synced VLANs
When an HSR master device is brought UP, it auto-adds VLAN 0 via vlan_vid0_add(), which propagates VID 0 to its slave devices (slave A and B).
If a slave device is later unregistered while HSR is active (e.g., during netns cleanup or interface destruction), hsr_del_port() is called to detach the slave port from the HSR master. However, hsr_del_port() currently does not delete the VLAN IDs that were synced to the slave device by HSR.
As a result, the slave device retains a refcount on VID 0 (and any other synced VLANs). When the slave device is destroyed, its vlan_info / vlan_vid_info structure remains allocated, leading to a memory leak.
Fix this by calling vlan_vids_del_by_dev(port->dev, master->dev) in hsr_del_port() before unlinking slave A or slave B ports, matching the propagation logic in hsr_ndo_vlan_rx_add_vid() / hsr_ndo_vlan_rx_kill_vid() and the cleanup behavior in bonding and team drivers.
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Analysis
by VulDB Data Team • 08/10/2026
The vulnerability described represents a memory management issue within the Linux kernel's High-availability Seamless Redundancy protocol implementation that falls under the category of memory leaks as classified by CWE-401. This flaw occurs specifically within the network driver subsystem where HSR master devices maintain synchronization of VLAN configurations with their slave interfaces. When an HSR master device is activated, it automatically propagates VLAN ID 0 to its associated slave devices through the vlan_vid0_add() function, establishing a reference relationship that should be properly maintained throughout the device lifecycle.
The technical flaw manifests during the cleanup phase when slave devices are unregistered while HSR remains active. The hsr_del_port() function is responsible for detaching these slave ports from the HSR master but fails to properly remove the VLAN identifiers that were synchronized to the slave interfaces. This incomplete cleanup leaves the slave device holding references to VLAN IDs including VID 0, which creates a dangling reference scenario where memory allocated for vlan_info and vlan_vid_info structures remains unreleased even after the slave device has been destroyed. The memory leak occurs because the kernel's reference counting mechanism prevents deallocation of these structures while references remain active.
The operational impact of this vulnerability extends beyond simple memory consumption issues as it can lead to progressive system resource exhaustion over time, particularly in environments where network interfaces are frequently created and destroyed during dynamic network management operations or namespace cleanup processes. The vulnerability affects systems running Linux kernels with HSR support and is especially concerning in high-availability network configurations where interface lifecycle management is frequent. This issue aligns with ATT&CK technique T1490 for resource exhaustion attacks, as the memory leak can potentially be exploited to consume system resources and degrade performance.
The proposed fix addresses this vulnerability by implementing proper VLAN cleanup within the hsr_del_port() function through the addition of vlan_vids_del_by_dev(port->dev, master->dev) call before the slave port is unlinked from the HSR master. This approach mirrors the established patterns found in other network driver implementations such as bonding and team drivers, ensuring consistency with existing kernel networking practices. The solution follows the same propagation logic that exists in hsr_ndo_vlan_rx_add_vid() and hsr_ndo_vlan_rx_kill_vid() functions, creating a symmetric cleanup mechanism that maintains proper reference counting throughout the VLAN synchronization process. This remediation ensures that when slave devices are destroyed, all synchronized VLAN references are properly removed, allowing the kernel's memory management subsystem to correctly deallocate the associated structures and prevent the accumulation of leaked memory resources.
The fix demonstrates adherence to secure coding practices by maintaining proper resource cleanup semantics and follows established kernel networking patterns that have been validated through extensive testing in similar driver implementations. The solution maintains backward compatibility while addressing the specific memory leak scenario without disrupting normal HSR operation or introducing new attack vectors. This remediation approach also aligns with security best practices for kernel module development, ensuring that all allocated resources are properly managed and released according to established reference counting principles that prevent both memory leaks and use-after-free conditions in the network subsystem.