CVE-2026-63905 Affecting kernel-kvmsmall package, versions <6.12.0-160000.37.1


Severity

Recommended
0.0
medium
0
10

Based on SUSE Linux Enterprise Server security rating.

Threat Intelligence

EPSS
0.22% (13th percentile)

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  • Snyk IDSNYK-SLES1600-KERNELKVMSMALL-19336088
  • published27 Aug 2026
  • disclosed11 Aug 2026

Introduced: 11 Aug 2026

NewCVE-2026-63905  (opens in a new tab)

How to fix?

Upgrade SLES:16.0.0 kernel-kvmsmall to version 6.12.0-160000.37.1 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream kernel-kvmsmall package and not the kernel-kvmsmall package as distributed by SLES. See How to fix? for SLES:16.0.0 relevant fixed versions and status.

In the Linux kernel, the following vulnerability has been resolved:

usbip: vudc: Fix use after free bug in vudc_remove due to race condition

This patch follows up Zheng Wang's 2023 report of a use-after-free in vudc_remove(). The original thread stalled on Shuah Khan's request for runtime testing of the unplug/unbind path. This patch supplies that testing and keeps Zheng's original fix shape.

In vudc_probe(), v_init_timer() binds udc->tr_timer.timer to v_timer(). usbip_sockfd_store() starts the timer via v_start_timer()/v_kick_timer(). vudc_remove() can then free the containing struct vudc while the timer is still pending or executing.

KASAN confirms the race on an unpatched x86_64 QEMU guest with CONFIG_KASAN=y, CONFIG_USBIP_VUDC=y, CONFIG_USB_ZERO=y, and a tight loop that repeatedly writes a socket fd to usbip_sockfd, closes the socket pair, and unbinds/rebinds usbip-vudc.0:

BUG: KASAN: slab-use-after-free in __run_timer_base.part.0+0x8ba/0x8e0 Write of size 8 at addr ffff888001b80740 by task trigger_and_unb/239 Allocated by task 239: vudc_probe+0x4d/0xaa0 Freed by task 239: kfree+0x18f/0x520 device_release_driver_internal+0x388/0x540 unbind_store+0xd9/0x100

This lands in the timer core rather than v_timer() itself because the embedded timer_list is being walked after its containing struct vudc has already been freed. The underlying lifetime bug is the same one Zheng reported.

With v_stop_timer() called from vudc_remove() and the timer deleted synchronously, the same harness completed 5000 bind/unbind iterations with no KASAN report.

CVSS Base Scores

version 3.1