# CVE-2022-50220: linux: In the Linux kernel, the following vulnerability has been resolved:  usbnet: Fix linkwatch use-after-free on disconne...

CVE-2022-50220 is fixed in linux on 1 platform, first by DEBIAN-CVE-2022-50220, released June 18, 2025. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2022-50220
- Priority: High
- CVSS: 7.8 (high)
- EPSS: 0.0025
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Jun 18, 2025

## Description

In the Linux kernel, the following vulnerability has been resolved:  usbnet: Fix linkwatch use-after-free on disconnect  usbnet uses the work usbnet_deferred_kevent() to perform tasks which may sleep.  On disconnect, completion of the work was originally awaited in ->ndo_stop().  But in 2003, that was moved to ->disconnect() by historic commit "[PATCH] USB: usbnet, prevent exotic rtnl deadlock":    https://git.kernel.org/tglx/history/c/0f138bbfd83c  The change was made because back then, the kernel's workqueue implementation did not allow waiting for a single work.  One had to wait for completion of *all* work by calling flush_scheduled_work(), and that could deadlock when waiting for usbnet_deferred_kevent() with rtnl_mutex held in ->ndo_stop().  The commit solved one problem but created another:  It causes a use-after-free in USB Ethernet drivers aqc111.c, asix_devices.c, ax88179_178a.c, ch9200.c and smsc75xx.c:  * If the drivers receive a link change interrupt immediately before   disconnect, they raise EVENT_LINK_RESET in their (non-sleepable)   ->status() callback and schedule usbnet_deferred_kevent(). * usbnet_deferred_kevent() invokes the driver's ->link_reset() callback,   which calls netif_carrier_{on,off}(). * That in turn schedules the work linkwatch_event().  Because usbnet_deferred_kevent() is awaited after unregister_netdev(), netif_carrier_{on,off}() may operate on an unregistered netdev and linkwatch_event() may run after free_netdev(), causing a use-after-free.  In 2010, usbnet was changed to only wait for a single instance of usbnet_deferred_kevent() instead of *all* work by commit 23f333a2bfaf ("drivers/net: don't use flush_scheduled_work()").  Unfortunately the commit neglected to move the wait back to ->ndo_stop().  Rectify that omission at long last.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 12.15 (bookworm) | 6.0.2-1 | [DEBIAN-CVE-2022-50220](https://patchblox.com/security/data/fix/linux/debian-cve-2022-50220.md) | Jun 18, 2025 |
| Linux | linux Debian 13.5 (trixie) | 6.0.2-1 | [DEBIAN-CVE-2022-50220](https://patchblox.com/security/data/fix/linux/debian-cve-2022-50220.md) | Jun 18, 2025 |
| Linux | linux Debian 14 | 6.0.2-1 | [DEBIAN-CVE-2022-50220](https://patchblox.com/security/data/fix/linux/debian-cve-2022-50220.md) | Jun 18, 2025 |

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