# CVE-2026-43421: usb: gadget: f_ncm: Fix net_device lifecycle with device_move

CVE-2026-43421 is fixed in linux on 1 platform, first by DEBIAN-CVE-2026-43421, released May 15, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-43421
- Priority: Routine
- CVSS: 5.5 (medium)
- EPSS: 0.0012
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: May 8, 2026
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-43421

## 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/f2a4f9847617a0929d62025748384092e5f35cce.camel@crapouillou.net/ [2] https://lore.kernel.org/linux-usb/795ea759-7eaf-4f78-81f4-01ffbf2d7961@ixit.cz/

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 12.15 (bookworm) | 6.1.176-1 | [DEBIAN-CVE-2026-43421](https://patchblox.com/security/data/fix/linux/debian-cve-2026-43421.md) | May 15, 2026 |
| Linux | linux Debian 13.5 (trixie) | 6.12.85-1 | [DEBIAN-CVE-2026-43421](https://patchblox.com/security/data/fix/linux/debian-cve-2026-43421.md) | May 15, 2026 |
| Linux | linux Debian 14 | 6.19.10-1 | [DEBIAN-CVE-2026-43421](https://patchblox.com/security/data/fix/linux/debian-cve-2026-43421.md) | May 15, 2026 |

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Data as of 2026-11-09T19:38:12Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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