CVE-2026-43327 (GCVE-0-2026-43327)

Vulnerability from cvelistv5 – Published: 2026-05-08 13:31 – Updated: 2026-05-08 13:31
VLAI?
Title
USB: dummy-hcd: Fix locking/synchronization error
Summary
In the Linux kernel, the following vulnerability has been resolved: USB: dummy-hcd: Fix locking/synchronization error Syzbot testing was able to provoke an addressing exception and crash in the usb_gadget_udc_reset() routine in drivers/usb/gadgets/udc/core.c, resulting from the fact that the routine was called with a second ("driver") argument of NULL. The bad caller was set_link_state() in dummy_hcd.c, and the problem arose because of a race between a USB reset and driver unbind. These sorts of races were not supposed to be possible; commit 7dbd8f4cabd9 ("USB: dummy-hcd: Fix erroneous synchronization change"), along with a few followup commits, was written specifically to prevent them. As it turns out, there are (at least) two errors remaining in the code. Another patch will address the second error; this one is concerned with the first. The error responsible for the syzbot crash occurred because the stop_activity() routine will sometimes drop and then re-acquire the dum->lock spinlock. A call to stop_activity() occurs in set_link_state() when handling an emulated USB reset, after the test of dum->ints_enabled and before the increment of dum->callback_usage. This allowed another thread (doing a driver unbind) to sneak in and grab the spinlock, and then clear dum->ints_enabled and dum->driver. Normally this other thread would have to wait for dum->callback_usage to go down to 0 before it would clear dum->driver, but in this case it didn't have to wait since dum->callback_usage had not yet been incremented. The fix is to increment dum->callback_usage _before_ calling stop_activity() instead of after. Then the thread doing the unbind will not clear dum->driver until after the call to usb_gadget_udc_reset() safely returns and dum->callback_usage has been decremented again.
Severity ?
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 7dbd8f4cabd96db5a50513de9d83a8105a5ffc81 , < 6350c7dd33ab481ef41c931a238361490c32d15c (git)
Affected: 7dbd8f4cabd96db5a50513de9d83a8105a5ffc81 , < cc97fb5969177cccce2e23b31298df220fc7570d (git)
Affected: 7dbd8f4cabd96db5a50513de9d83a8105a5ffc81 , < 218886b2ef2dea7627d3700ab0abaf4bf9d1161f (git)
Affected: 7dbd8f4cabd96db5a50513de9d83a8105a5ffc81 , < 791966f85b439b261bf19865cf1c07c065ffb4b4 (git)
Affected: 7dbd8f4cabd96db5a50513de9d83a8105a5ffc81 , < 805b1833d6ed6da5086e610578a28e71bb54fbbb (git)
Affected: 7dbd8f4cabd96db5a50513de9d83a8105a5ffc81 , < efbd9441f1e769a7aae1813d497cec09cbdff031 (git)
Affected: 7dbd8f4cabd96db5a50513de9d83a8105a5ffc81 , < 69ab97a693251d6a6093e630060a3c744fd58524 (git)
Affected: 7dbd8f4cabd96db5a50513de9d83a8105a5ffc81 , < 616a63ff495df12863692ab3f9f7b84e3fa7a66d (git)
Affected: 7b416b9dac6ede26d4ca0c1a88b448b543623ff3 (git)
Affected: 8590bc1da625dd4a589eac0fc3aa3cf4f400424d (git)
Affected: a867d5b932ac4911d3f8a1e63505061b0c81f889 (git)
Affected: e84b4a008365b7edbd842a063ae28d040a98db25 (git)
Affected: e39b17143a5b5aac81f066d455e5d3a9877eb3ae (git)
Affected: 4f8ae1fcb0dfbb72a7678f81bf01fb7fc85c6715 (git)
Create a notification for this product.
    Linux Linux Affected: 4.14
Unaffected: 0 , < 4.14 (semver)
Unaffected: 5.10.253 , ≤ 5.10.* (semver)
Unaffected: 5.15.203 , ≤ 5.15.* (semver)
Unaffected: 6.1.168 , ≤ 6.1.* (semver)
Unaffected: 6.6.134 , ≤ 6.6.* (semver)
Unaffected: 6.12.81 , ≤ 6.12.* (semver)
Unaffected: 6.18.22 , ≤ 6.18.* (semver)
Unaffected: 6.19.12 , ≤ 6.19.* (semver)
Unaffected: 7.0 , ≤ * (original_commit_for_fix)
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        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nUSB: dummy-hcd: Fix locking/synchronization error\n\nSyzbot testing was able to provoke an addressing exception and crash\nin the usb_gadget_udc_reset() routine in\ndrivers/usb/gadgets/udc/core.c, resulting from the fact that the\nroutine was called with a second (\"driver\") argument of NULL.  The bad\ncaller was set_link_state() in dummy_hcd.c, and the problem arose\nbecause of a race between a USB reset and driver unbind.\n\nThese sorts of races were not supposed to be possible; commit\n7dbd8f4cabd9 (\"USB: dummy-hcd: Fix erroneous synchronization change\"),\nalong with a few followup commits, was written specifically to prevent\nthem.  As it turns out, there are (at least) two errors remaining in\nthe code.  Another patch will address the second error; this one is\nconcerned with the first.\n\nThe error responsible for the syzbot crash occurred because the\nstop_activity() routine will sometimes drop and then re-acquire the\ndum-\u003elock spinlock.  A call to stop_activity() occurs in\nset_link_state() when handling an emulated USB reset, after the test\nof dum-\u003eints_enabled and before the increment of dum-\u003ecallback_usage.\nThis allowed another thread (doing a driver unbind) to sneak in and\ngrab the spinlock, and then clear dum-\u003eints_enabled and dum-\u003edriver.\nNormally this other thread would have to wait for dum-\u003ecallback_usage\nto go down to 0 before it would clear dum-\u003edriver, but in this case it\ndidn\u0027t have to wait since dum-\u003ecallback_usage had not yet been\nincremented.\n\nThe fix is to increment dum-\u003ecallback_usage _before_ calling\nstop_activity() instead of after.  Then the thread doing the unbind\nwill not clear dum-\u003edriver until after the call to\nusb_gadget_udc_reset() safely returns and dum-\u003ecallback_usage has been\ndecremented again."
        }
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      "providerMetadata": {
        "dateUpdated": "2026-05-08T13:31:12.896Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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          "url": "https://git.kernel.org/stable/c/6350c7dd33ab481ef41c931a238361490c32d15c"
        },
        {
          "url": "https://git.kernel.org/stable/c/cc97fb5969177cccce2e23b31298df220fc7570d"
        },
        {
          "url": "https://git.kernel.org/stable/c/218886b2ef2dea7627d3700ab0abaf4bf9d1161f"
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        {
          "url": "https://git.kernel.org/stable/c/791966f85b439b261bf19865cf1c07c065ffb4b4"
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        {
          "url": "https://git.kernel.org/stable/c/805b1833d6ed6da5086e610578a28e71bb54fbbb"
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        },
        {
          "url": "https://git.kernel.org/stable/c/616a63ff495df12863692ab3f9f7b84e3fa7a66d"
        }
      ],
      "title": "USB: dummy-hcd: Fix locking/synchronization error",
      "x_generator": {
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-43327",
    "datePublished": "2026-05-08T13:31:12.896Z",
    "dateReserved": "2026-05-01T14:12:56.002Z",
    "dateUpdated": "2026-05-08T13:31:12.896Z",
    "state": "PUBLISHED"
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  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-43327",
      "date": "2026-05-09",
      "epss": "0.00024",
      "percentile": "0.07036"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-43327\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2026-05-08T14:16:42.243\",\"lastModified\":\"2026-05-08T14:16:42.243\",\"vulnStatus\":\"Received\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\nUSB: dummy-hcd: Fix locking/synchronization error\\n\\nSyzbot testing was able to provoke an addressing exception and crash\\nin the usb_gadget_udc_reset() routine in\\ndrivers/usb/gadgets/udc/core.c, resulting from the fact that the\\nroutine was called with a second (\\\"driver\\\") argument of NULL.  The bad\\ncaller was set_link_state() in dummy_hcd.c, and the problem arose\\nbecause of a race between a USB reset and driver unbind.\\n\\nThese sorts of races were not supposed to be possible; commit\\n7dbd8f4cabd9 (\\\"USB: dummy-hcd: Fix erroneous synchronization change\\\"),\\nalong with a few followup commits, was written specifically to prevent\\nthem.  As it turns out, there are (at least) two errors remaining in\\nthe code.  Another patch will address the second error; this one is\\nconcerned with the first.\\n\\nThe error responsible for the syzbot crash occurred because the\\nstop_activity() routine will sometimes drop and then re-acquire the\\ndum-\u003elock spinlock.  A call to stop_activity() occurs in\\nset_link_state() when handling an emulated USB reset, after the test\\nof dum-\u003eints_enabled and before the increment of dum-\u003ecallback_usage.\\nThis allowed another thread (doing a driver unbind) to sneak in and\\ngrab the spinlock, and then clear dum-\u003eints_enabled and dum-\u003edriver.\\nNormally this other thread would have to wait for dum-\u003ecallback_usage\\nto go down to 0 before it would clear dum-\u003edriver, but in this case it\\ndidn\u0027t have to wait since dum-\u003ecallback_usage had not yet been\\nincremented.\\n\\nThe fix is to increment dum-\u003ecallback_usage _before_ calling\\nstop_activity() instead of after.  Then the thread doing the unbind\\nwill not clear dum-\u003edriver until after the call to\\nusb_gadget_udc_reset() safely returns and dum-\u003ecallback_usage has been\\ndecremented again.\"}],\"metrics\":{},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/218886b2ef2dea7627d3700ab0abaf4bf9d1161f\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/616a63ff495df12863692ab3f9f7b84e3fa7a66d\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/6350c7dd33ab481ef41c931a238361490c32d15c\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/69ab97a693251d6a6093e630060a3c744fd58524\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/791966f85b439b261bf19865cf1c07c065ffb4b4\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/805b1833d6ed6da5086e610578a28e71bb54fbbb\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/cc97fb5969177cccce2e23b31298df220fc7570d\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/efbd9441f1e769a7aae1813d497cec09cbdff031\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}"
  }
}


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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



Detection rules are retrieved from Rulezet.