CVE-2026-43327
Estado: AnalizadaMedia (5.5)—
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.
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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.
CVSS
- Versión: 3.1
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- Puntuación base: 5.5
Probabilidad de explotación (EPSS)
- Probabilidad de explotación en los próximos 30 días: 0.13%
- Percentil entre todas las CVEs puntuadas: 2
- Fecha de la puntuación: 5/10/2026
EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).
Tecnologías afectadas (1)
CWE
- CWE-667
Referencias
- https://git.kernel.org/stable/c/218886b2ef2dea7627d3700ab0abaf4bf9d1161f
- https://git.kernel.org/stable/c/616a63ff495df12863692ab3f9f7b84e3fa7a66d
- https://git.kernel.org/stable/c/6350c7dd33ab481ef41c931a238361490c32d15c
- https://git.kernel.org/stable/c/69ab97a693251d6a6093e630060a3c744fd58524
- https://git.kernel.org/stable/c/791966f85b439b261bf19865cf1c07c065ffb4b4
- https://git.kernel.org/stable/c/805b1833d6ed6da5086e610578a28e71bb54fbbb
- https://git.kernel.org/stable/c/cc97fb5969177cccce2e23b31298df220fc7570d
- https://git.kernel.org/stable/c/efbd9441f1e769a7aae1813d497cec09cbdff031
JSON original (NVD)
Mostrar
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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->lock spinlock. A call to stop_activity() occurs in\nset_link_state() when handling an emulated USB reset, after the test\nof dum->ints_enabled and before the increment of dum->callback_usage.\nThis allowed another thread (doing a driver unbind) to sneak in and\ngrab the spinlock, and then clear dum->ints_enabled and dum->driver.\nNormally this other thread would have to wait for dum->callback_usage\nto go down to 0 before it would clear dum->driver, but in this case it\ndidn't have to wait since dum->callback_usage had not yet been\nincremented.\n\nThe fix is to increment dum->callback_usage _before_ calling\nstop_activity() instead of after. Then the thread doing the unbind\nwill not clear dum->driver until after the call to\nusb_gadget_udc_reset() safely returns and dum->callback_usage has been\ndecremented again."
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