CVE-2026-63905 (GCVE-0-2026-63905)
Vulnerability from cvelistv5
Published
2026-07-19 14:55
Modified
2026-07-19 14:55
Severity ?
Summary
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.
References
Impacted products
Vendor Product Version
Linux Linux Version: b6a0ca11186759ad7045d68a5447b1e89f658384
Version: b6a0ca11186759ad7045d68a5447b1e89f658384
Version: b6a0ca11186759ad7045d68a5447b1e89f658384
Version: b6a0ca11186759ad7045d68a5447b1e89f658384
Version: b6a0ca11186759ad7045d68a5447b1e89f658384
Version: b6a0ca11186759ad7045d68a5447b1e89f658384
Version: b6a0ca11186759ad7045d68a5447b1e89f658384
Version: b6a0ca11186759ad7045d68a5447b1e89f658384
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{
  "containers": {
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        {
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          "product": "Linux",
          "programFiles": [
            "drivers/usb/usbip/vudc_dev.c",
            "drivers/usb/usbip/vudc_transfer.c"
          ],
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      ],
      "cpeApplicability": [
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      ],
      "descriptions": [
        {
          "lang": "en",
          "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\u0027s 2023 report of a use-after-free in\nvudc_remove(). The original thread stalled on Shuah Khan\u0027s request for\nruntime testing of the unplug/unbind path. This patch supplies that\ntesting and keeps Zheng\u0027s original fix shape.\n\nIn vudc_probe(), v_init_timer() binds udc-\u003etr_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."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-07-19T14:55:12.270Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/61704e5cf9cd7464b510eb606e7e2978b1160a64"
        },
        {
          "url": "https://git.kernel.org/stable/c/dcc1c90b28b28b7c493547506297e78653f81952"
        },
        {
          "url": "https://git.kernel.org/stable/c/1036ac6148995feaf486014d32bf26bf993c06a9"
        },
        {
          "url": "https://git.kernel.org/stable/c/a0638db2340ee053ab0450656a763fd111475e54"
        },
        {
          "url": "https://git.kernel.org/stable/c/d07ed707467ce05ea9c03412d0c5ee9d0fe386a6"
        },
        {
          "url": "https://git.kernel.org/stable/c/88d459e5b5a46da1ef9fd6f52d9439343edeec88"
        },
        {
          "url": "https://git.kernel.org/stable/c/207bf80362df3fce8ebc9723351dcb1bc6d9ed0f"
        },
        {
          "url": "https://git.kernel.org/stable/c/d96209626a29ea64666be98c30b30ac82e5f1be6"
        }
      ],
      "title": "usbip: vudc: Fix use after free bug in vudc_remove due to race condition",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-63905",
    "datePublished": "2026-07-19T14:55:12.270Z",
    "dateReserved": "2026-07-19T07:54:57.020Z",
    "dateUpdated": "2026-07-19T14:55:12.270Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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