CVE-2026-64455 in Linux
Summary
by MITRE • 07/25/2026
In the Linux kernel, the following vulnerability has been resolved:
USB: chaoskey: Fix slab-use-after-free in chaoskey_release()
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 usb_interface structure after it has been deallocated:
BUG: KASAN: slab-use-after-free in dev_driver_string (drivers/base/core.c:2406) Read of size 8 at addr ffff888168e8a0b8 by task chaoskey_raw_re/10106
Hardware name: QEMU Ubuntu 24.04 PC v2 (i440FX + PIIX, arch_caps fix, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 Call Trace: <TASK> dump_stack_lvl (lib/dump_stack.c:94 lib/dump_stack.c:120) print_report (mm/kasan/report.c:378 mm/kasan/report.c:482) kasan_report (mm/kasan/report.c:595) dev_driver_string (drivers/base/core.c:2406) __dynamic_dev_dbg (lib/dynamic_debug.c:906) chaoskey_release (drivers/usb/misc/chaoskey.c:323) __fput (fs/file_table.c:510) fput_close_sync (fs/file_table.c:615) __x64_sys_close (fs/open.c:1507 fs/open.c:1492 fs/open.c:1492) do_syscall_64 (arch/x86/entry/syscall_64.c:63 arch/x86/entry/syscall_64.c:94) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121)
The driver's last reference to the interface structure is dropped in the chaoskey_free() 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.
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Analysis
by VulDB Data Team • 07/25/2026
The vulnerability described represents a critical use-after-free condition within the Linux kernel's chaoskey USB driver implementation. This flaw manifests during the device release process when a user closes the device file after the underlying USB device has already been disconnected from the system. The issue stems from improper memory management practices where debugging log statements attempt to access a usb_interface structure that has already been deallocated by the kernel's memory subsystem. Such conditions create exploitable entry points for malicious actors seeking to manipulate kernel memory structures or escalate privileges through controlled memory corruption attacks.
The technical root cause of this vulnerability aligns with CWE-416, which specifically addresses use-after-free vulnerabilities in software systems. The flaw occurs in the chaoskey_release() function within drivers/usb/misc/chaoskey.c at line 323, where a call to dev_driver_string() attempts to dereference a pointer to an already freed structure. This memory access violation is detected by KASAN (Kernel Address Sanitizer) which identifies the slab-use-after-free condition during kernel execution. The call trace demonstrates how the error propagates through the standard kernel execution path including file descriptor closure routines and system call handling mechanisms, ultimately leading to a kernel panic or potential security compromise.
The operational impact of this vulnerability extends beyond simple system instability, as it represents a potential privilege escalation vector within kernel space. When an attacker can control the timing of device disconnection followed by file descriptor closure, they may exploit the use-after-free condition to execute arbitrary code with kernel privileges. This scenario particularly affects systems running vulnerable kernel versions where USB devices are frequently connected and disconnected, creating opportunities for exploitation through malicious device drivers or crafted user-space applications that manipulate device lifecycle events.
The recommended mitigation strategy involves removing the problematic debugging statement from the chaoskey_release() function since the access occurs within an unimportant log message rather than functional code. This approach directly addresses the immediate vulnerability without altering core driver functionality or performance characteristics. The fix aligns with established security practices for handling kernel memory management and demonstrates proper defensive programming techniques. System administrators should ensure all affected systems are updated to patched kernel versions that contain this specific remediation, particularly in environments where USB device management occurs frequently or where untrusted users have access to device file operations.
The vulnerability also highlights important considerations regarding kernel debugging statements and their interaction with memory management systems. Even seemingly innocuous debug code can create security risks when not properly synchronized with resource lifecycle management. This particular case demonstrates how the kernel's device core manages reference counting and cleanup operations, where the chaoskey_free() routine properly drops the final reference to the usb_interface structure but subsequent debugging code fails to respect this memory state transition. The issue underscores the importance of thorough testing of driver release routines and proper synchronization between resource management and logging operations in kernel space.
This vulnerability classification places it within the broader ATT&CK framework under techniques related to privilege escalation and kernel exploitation, specifically targeting the kernel's memory management subsystem. The remediation approach reflects standard practices for addressing use-after-free conditions in operating system kernels while maintaining backward compatibility and driver functionality. The fix demonstrates the principle of least privilege in kernel programming where debug code should not interfere with proper resource cleanup procedures, particularly when dealing with potentially concurrent access patterns that could lead to memory corruption conditions.