FKIE_CVE-2026-43327

Vulnerability from fkie_nvd - Published: 2026-05-08 14:16 - Updated: 2026-05-15 18:05
Severity
5.5 (Medium) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
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.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/218886b2ef2dea7627d3700ab0abaf4bf9d1161fPatch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/616a63ff495df12863692ab3f9f7b84e3fa7a66dPatch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/6350c7dd33ab481ef41c931a238361490c32d15cPatch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/69ab97a693251d6a6093e630060a3c744fd58524Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/791966f85b439b261bf19865cf1c07c065ffb4b4Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/805b1833d6ed6da5086e610578a28e71bb54fbbbPatch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/cc97fb5969177cccce2e23b31298df220fc7570dPatch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/efbd9441f1e769a7aae1813d497cec09cbdff031Patch
Impacted products
Vendor Product Version
linux linux_kernel *
linux linux_kernel *
linux linux_kernel *
linux linux_kernel *
linux linux_kernel *
linux linux_kernel *
linux linux_kernel *
linux linux_kernel *
linux linux_kernel *
linux linux_kernel *
linux linux_kernel *
linux linux_kernel *
linux linux_kernel 7.0
linux linux_kernel 7.0
linux linux_kernel 7.0
linux linux_kernel 7.0
linux linux_kernel 7.0
linux linux_kernel 7.0
linux linux_kernel 7.0
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      "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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  "id": "CVE-2026-43327",
  "lastModified": "2026-05-15T18:05:56.443",
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          "attackVector": "LOCAL",
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          "baseScore": 5.5,
          "baseSeverity": "MEDIUM",
          "confidentialityImpact": "NONE",
          "integrityImpact": "NONE",
          "privilegesRequired": "LOW",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
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  "published": "2026-05-08T14:16:42.243",
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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

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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.