CVE-2026-43324 USB: dummy-hcd: Fix interrupt synchronization error
A race condition in the Linux kernel's dummy-hcd USB driver can cause a callback handler to run during unbinding, potentially leading to system instability or crashes.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-43324?
CVE-2026-43324 is a high-severity vulnerability in Linux kernel, published on 8 May 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
USB: dummy-hcd: Fix interrupt synchronization error
This fixes an error in synchronization in the dummy-hcd driver. The error has a somewhat involved history. The synchronization mechanism was introduced by commit 7dbd8f4cabd9 ("USB: dummy-hcd: Fix erroneous synchronization change"), which added an emulated "interrupts enabled" flag together with code emulating synchronize_irq() (it waits until all current handler callbacks have returned).
But the emulated interrupt-disable occurred too late, after the driver containing the handler callback routines had been told that it was unbound and no more callbacks would occur. Commit 4a5d797a9f9c ("usb: gadget: dummy_hcd: fix gpf in gadget_setup") tried to fix this by moving the synchronize_irq() emulation code from dummy_stop() to dummy_pullup(), which runs before the unbind callback.
There still were races, though, because the emulated interrupt-disable still occurred too late. It couldn't be moved to dummy_pullup(), because that routine can be called for reasons other than an impending unbind. Therefore commits 7dc0c55e9f30 ("USB: UDC core: Add udc_async_callbacks gadget op") and 04145a03db9d ("USB: UDC: Implement udc_async_callbacks in dummy-hcd") added an API allowing the UDC core to tell dummy-hcd exactly when emulated interrupts and their callbacks should be disabled.
That brings us to the current state of things, which is still wrong because the emulated synchronize_irq() occurs before the emulated interrupt-disable! That's no good, beause it means that more emulated interrupts can occur after the synchronize_irq() emulation has run, leading to the possibility that a callback handler may be running when the gadget driver is unbound.
To fix this, we have to move the synchronize_irq() emulation code yet again, to the dummy_udc_async_callbacks() routine, which takes care of enabling and disabling emulated interrupt requests. The synchronization will now run immediately after emulated interrupts are disabled, which is where it belongs.
Which versions are affected by CVE-2026-43324?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-43324?
Apply the vendor's patch.
Is CVE-2026-43324 being exploited?
There is no known exploitation of CVE-2026-43324 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2026-43324, DEBIAN-CVE-2026-43324, GHSA-4f56-4jhm-5934, ROOT-OS-UBUNTU-2204-CVE-2026-43324, ROOT-OS-UBUNTU-2404-CVE-2026-43324, UBUNTU-CVE-2026-43324.