CVE-2026-63905
Full vulnerability record from the local CVENow database.
Description
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.
Severity
HIGH
CVSS score
7.8
(v3.1)
Vulnerability status
Analyzed
Source identifier
416baaa9-dc9f-4396-8d5f-8c081fb06d67
Published
2026-07-19 16:17:08.260000
Last modified
2026-10-30 14:37:32.330000
View original CVE JSON
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"id": "CVE-2026-63905",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"published": "2026-07-19T16:17:08.260",
"lastModified": "2026-10-30T14:37:32.330",
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"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nusbip: vudc: Fix use after free bug in vudc_remove due to race condition\n\nThis patch follows up Zheng Wang's 2023 report of a use-after-free in\nvudc_remove(). The original thread stalled on Shuah Khan's request for\nruntime testing of the unplug/unbind path. This patch supplies that\ntesting and keeps Zheng's original fix shape.\n\nIn vudc_probe(), v_init_timer() binds udc->tr_timer.timer to v_timer().\nusbip_sockfd_store() starts the timer via v_start_timer()/v_kick_timer().\nvudc_remove() can then free the containing struct vudc while the timer is\nstill pending or executing.\n\nKASAN confirms the race on an unpatched x86_64 QEMU guest with\nCONFIG_KASAN=y, CONFIG_USBIP_VUDC=y, CONFIG_USB_ZERO=y, and a tight loop\nthat repeatedly writes a socket fd to usbip_sockfd, closes the socket\npair, and unbinds/rebinds usbip-vudc.0:\n\n BUG: KASAN: slab-use-after-free in __run_timer_base.part.0+0x8ba/0x8e0\n Write of size 8 at addr ffff888001b80740 by task trigger_and_unb/239\n Allocated by task 239:\n vudc_probe+0x4d/0xaa0\n Freed by task 239:\n kfree+0x18f/0x520\n device_release_driver_internal+0x388/0x540\n unbind_store+0xd9/0x100\n\nThis lands in the timer core rather than v_timer() itself because the\nembedded timer_list is being walked after its containing struct vudc has\nalready been freed. The underlying lifetime bug is the same one Zheng\nreported.\n\nWith v_stop_timer() called from vudc_remove() and the timer deleted\nsynchronously, the same harness completed 5000 bind/unbind iterations\nwith no KASAN report."
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