CVE-2026-43421
Received Received - Intake
USB Gadget NCM Net Device Lifecycle Fix

Publication date: 2026-05-08

Last updated on: 2026-05-08

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: usb: gadget: f_ncm: Fix net_device lifecycle with device_move The network device outlived its parent gadget device during disconnection, resulting in dangling sysfs links and null pointer dereference problems. A prior attempt to solve this by removing SET_NETDEV_DEV entirely [1] was reverted due to power management ordering concerns and a NO-CARRIER regression. A subsequent attempt to defer net_device allocation to bind [2] broke 1:1 mapping between function instance and network device, making it impossible for configfs to report the resolved interface name. This results in a regression where the DHCP server fails on pmOS. Use device_move to reparent the net_device between the gadget device and /sys/devices/virtual/ across bind/unbind cycles. This preserves the network interface across USB reconnection, allowing the DHCP server to retain their binding. Introduce gether_attach_gadget()/gether_detach_gadget() helpers and use __free(detach_gadget) macro to undo attachment on bind failure. The bind_count ensures device_move executes only on the first bind. [1] https://lore.kernel.org/lkml/[email protected]/ [2] https://lore.kernel.org/linux-usb/[email protected]/
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Meta Information
Published
2026-05-08
Last Modified
2026-05-08
Generated
2026-05-09
AI Q&A
2026-05-08
EPSS Evaluated
N/A
NVD
CVE-2026-43421
EUVD
EUVD-2026-28727
Affected Vendors & Products
Showing 1 associated CPE
Vendor Product Version / Range
linux linux_kernel *
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-UNKNOWN
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AI Powered Q&A
Can you explain this vulnerability to me?

This vulnerability exists in the Linux kernel's USB gadget function for network control model (f_ncm). It occurs because the network device (net_device) outlives its parent gadget device during disconnection, which leads to dangling sysfs links and null pointer dereference issues.

Previous attempts to fix this problem either caused regressions related to power management or broke the one-to-one mapping between the function instance and the network device, which affected DHCP server functionality.

The final fix uses device_move to reparent the net_device between the gadget device and /sys/devices/virtual/ during bind and unbind cycles. This preserves the network interface across USB reconnections and allows the DHCP server to maintain its binding.


How can this vulnerability impact me? :

This vulnerability can cause system instability due to null pointer dereferences when the network device outlives its parent gadget device during USB disconnection.

It can also lead to dangling sysfs links, which may cause unexpected behavior or errors in system management tools.

Additionally, improper handling of the network device lifecycle can break DHCP server functionality, potentially disrupting network connectivity on affected systems.


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