UBUNTU-CVE-2026-64455: Use After Free
In the Linux kernel, the following vulnerability has been resolved: USB: chaoskey: Fix slab-use-after-free in chaoskeyrelease() The chaoskey driver has a use-after-free bug in its release routine. If the user closes the device file after the USB device has been unplugged, a debugging log statement will try to access the usbinterface structure after it has been deallocated: BUG: KASAN: slab-use-after-free in devdriverstring (drivers/base/core.c:2406) Read of size 8 at addr ffff888168e8a0b8 by task chaoskeyrawre/10106 Hardware name: QEMU Ubuntu 24.04 PC v2 (i440FX + PIIX, archcaps fix, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 Call Trace: <TASK> dumpstacklvl (lib/dumpstack.c:94 lib/dumpstack.c:120) printreport (mm/kasan/report.c:378 mm/kasan/report.c:482) kasanreport (mm/kasan/report.c:595) devdriverstring (drivers/base/core.c:2406) dynamicdevdbg (lib/dynamicdebug.c:906) chaoskeyrelease (drivers/usb/misc/chaoskey.c:323) fput (fs/filetable.c:510) fputclosesync (fs/filetable.c:615) x64sysclose (fs/open.c:1507 fs/open.c:1492 fs/open.c:1492) dosyscall64 (arch/x86/entry/syscall64.c:63 arch/x86/entry/syscall64.c:94) entrySYSCALL64afterhwframe (arch/x86/entry/entry64.S:121) The driver's last reference to the interface structure is dropped in the chaoskeyfree() routine, so the code must not use the interface -- even in a debugging statement -- after that routine returns. (Exception: If we know that another reference is held by someone else, such as the device core while the disconnect routine runs, there's no problem. Thanks to Johan Hovold for pointing this out.) Since the bad access is part of an unimportant debugging statement, we can fix the problem simply by removing the whole statement.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
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ubuntu/linux-riscvto a version that resolves this vulnerability.Fixed in 7.0.0-31.31.1 - Compensating control
Remove the debugging log statement in chaoskey_release() that accesses the USB interface after chaoskey_free() returns.
Event History
Frequently Asked Questions
Which systems are exposed to this issue?
Exposure requires use of the Linux chaoskey USB driver with a ChaosKey device. The problematic path occurs when a process has the device file open, the USB device is unplugged, and the process subsequently closes the file.
What sequence triggers the use-after-free?
The USB device must be removed before the open device file is closed. During the close operation, the driver's debugging log path can access a USB interface structure that has already been deallocated.