medium CVSS 6.4 EPSS 0.33%

CVE-2023-52886·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: USB: core: Fix race by not overwriting udev->descriptor in hub_port_init() Syzbot reported an out-of-bounds read in sysfs.c:read_descriptors(): BUG: KASAN: slab-out-of-bounds in read_descriptors+0x263/0x280 drivers/usb/core/sysfs.c:883 Read of size 8 at addr ffff88801e78b8c8 by task udevd/5011 CPU: 0 PID: 5011 Comm: udevd Not tainted 6.4.0-rc6-syzkaller-00195-g40f71e7cd3c6 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/27/2023 Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xd9/0x150 lib/dump_stack.c:106 print_address_description.constprop.0+0x2c/0x3c0 mm/kasan/report.c:351 print_report mm/kasan/report.c:462 [inline] kasan_report+0x11c/0x130 mm/kasan/report.c:572 read_descriptors+0x263/0x280 drivers/usb/core/sysfs.c:883 ... Allocated by task 758: ... __do_kmalloc_node mm/slab_common.c:966 [inline] __kmalloc+0x5e/0x190 mm/slab_common.c:979 kmalloc include/linux/slab.h:563 [inline] kzalloc include/linux/slab.h:680 [inline] usb_get_configuration+0x1f7/0x5170 drivers/usb/core/config.c:887 usb_enumerate_device drivers/usb/core/hub.c:2407 [inline] usb_new_device+0x12b0/0x19d0 drivers/usb/core/hub.c:2545 As analyzed by Khazhy Kumykov, the cause of this bug is a race between read_descriptors() and hub_port_init(): The first routine uses a field in udev->descriptor, not expecting it to change, while the second overwrites it. Prior to commit 45bf39f8df7f ("USB: core: Don't hold device lock while reading the "descriptors" sysfs file") this race couldn't occur, because the routines were mutually exclusive thanks to the device locking. Removing that locking from read_descriptors() exposed it to the race. The best way to fix the bug is to keep hub_port_init() from changing udev->descriptor once udev has been initialized and registered. Drivers expect the descriptors stored in the kernel to be immutable; we should not undermine this expectation. In fact, this change should have been made long ago. So now hub_port_init() will take an additional argument, specifying a buffer in which to store the device descriptor it reads. (If udev has not yet been initialized, the buffer pointer will be NULL and then hub_port_init() will store the device descriptor in udev as before.) This eliminates the data race responsible for the out-of-bounds read. The changes to hub_port_init() appear more extensive than they really are, because of indentation changes resulting from an attempt to avoid writing to other parts of the usb_device structure after it has been initialized. Similar changes should be made to the code that reads the BOS descriptor, but that can be handled in a separate patch later on. This patch is sufficient to fix the bug found by syzbot.

Severity
medium
Software
Kernel
Fixed in
6.5.3
Published

How likely is exploitation

FIRST's Exploit Prediction Scoring System puts the probability of this CVE being exploited in the next 30 days at 0.33% — higher than 25% of all published CVEs. EPSS is an independent forecast of exploitation, not a severity rating: it says nothing about how much damage a successful attack does, which is what a CVSS score measures.

Affected versions

From: 6.5

Until: 6.5.3

Fixed in: 6.5.3

How to fix this CVE

Update your Linux kernel to version 6.5.3 or later to resolve a critical race condition in USB device initialization. This vulnerability allows concurrent read operations to trigger out-of-bounds memory access when the kernel overwrites device descriptor data during hub port initialization. Apply the kernel update through your distribution's package manager and reboot your system.

sudo dnf update kernel

Defensia detects this vulnerability

How to check if you are affected

  1. Step 1: Check your installed kernel version by running: uname -r
  2. Step 2: Compare the output against version 6.5.3 — if your version is 6.5.0 through 6.5.2, your system is vulnerable
  3. Step 3: Search system logs for KASAN warnings related to USB descriptors: grep -i 'KASAN.*slab-out-of-bounds' /var/log/kern.log or journalctl -xe | grep -i KASAN
  4. Step 4: After applying the patch, verify the new kernel version with: uname -r and confirm it is 6.5.3 or higher

FAQ

What is CVE-2023-52886?

This vulnerability is a data race in the Linux kernel's USB subsystem where hub_port_init() unsafely overwrites USB device descriptor fields while concurrent threads (such as sysfs readers) may be accessing the same memory. The race condition leads to out-of-bounds reads and potential system instability.

Is CVE-2023-52886 being actively exploited?

No, CVE-2023-52886 is not listed in the CISA KEV catalog and no public exploits are currently available. However, the vulnerability can be triggered reliably under specific timing conditions involving USB device enumeration.

What versions of Kernel are affected by CVE-2023-52886?

Linux kernel versions 6.5.0 through 6.5.2 are affected. Version 6.5.3 and all later 6.5.x releases, as well as other major kernel branches, contain the fix.

How do I check if my server is vulnerable to CVE-2023-52886?

Run: uname -r — if the output shows kernel version between 6.5.0 and 6.5.2 inclusive, your system is vulnerable. Alternatively, use: dpkg -l | grep linux-image (Debian/Ubuntu) or rpm -q kernel (RHEL/CentOS) to list installed kernel versions.

Does Defensia detect CVE-2023-52886?

Yes — Defensia's CVE advisory scanner compares installed kernel package versions against the NVD database. If a vulnerable kernel version is detected on a monitored server, CVE-2023-52886 will appear in your dashboard with remediation steps and patch guidance.

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References

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