CVE-2026-43327: Linux kernel · USB: dummy-hcd: Fix locking/synchronization error
Affects Linux kernelSource GCVE Database
Not known to be exploited.
Data as of 11 Nov 2026, 23:24 UTC
Rated by Threat Radar · No CVSS score from NVD or the CNA
Thin evidence
One scorer or none- EPSS
- 0.09% chance of exploitation in 30 days – higher than 0% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Exploitation evidence
Disclosed: evidence found.
CVE published 8 May 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 11 Nov 2026.
What to do
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| Linux Linux | Affected
| Fixed in– |
Description
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
- git.kernel.org/stable/c/6350c7dd33ab481ef41c931a238361490c32d15c (opens in a new tab)
- git.kernel.org/stable/c/cc97fb5969177cccce2e23b31298df220fc7570d (opens in a new tab)
- git.kernel.org/stable/c/218886b2ef2dea7627d3700ab0abaf4bf9d1161f (opens in a new tab)
- git.kernel.org/stable/c/791966f85b439b261bf19865cf1c07c065ffb4b4 (opens in a new tab)
- git.kernel.org/stable/c/805b1833d6ed6da5086e610578a28e71bb54fbbb (opens in a new tab)
- git.kernel.org/stable/c/efbd9441f1e769a7aae1813d497cec09cbdff031 (opens in a new tab)
- git.kernel.org/stable/c/69ab97a693251d6a6093e630060a3c744fd58524 (opens in a new tab)
- git.kernel.org/stable/c/616a63ff495df12863692ab3f9f7b84e3fa7a66d (opens in a new tab)