CVE-2023-52764

What it actually does

Shift exponent larger than the width of a 32-bit integer in cpia1 set_flicker causes UBSAN-detected out-of-bounds shift when exposure.gain exceeds the number of bits available for left-shift of currentexp.

Why it matters to the business

Systems using the affected cpia1 USB camera driver may experience kernel instability or crashes when the driver processes certain exposure parameters, with low prevalence since the hardware is uncommon.

How an attack unfolds

An attacker with the ability to supply crafted parameters to the cpia1 driver (via a malicious or emulated USB device) triggers the oversized left-shift in set_flicker, leading to undefined behavior that may be leveraged for denial of service.

How to fix it

Update the Linux kernel to a version containing commit 69bba62600bd91d6b7c1e8ca181faf8ac64f7060 or later; apply the conditional check that prevents shifting by more than the width of the integer type.

How to confirm the fix worked

Confirm the presence of the added bounds check on the shift amount in drivers/media/usb/gspca/cpia1.c and verify that UBSAN no longer reports the shift-out-of-bounds for large gain values.

Typical attack path

1. Attach or emulate a cpia1-compatible USB camera device
2. Trigger set_flicker path with exposure.gain value exceeding 31
3. Cause integer shift-out-of-bounds resulting in kernel fault or undefined behavior

How to detect it

Inspect kernel logs for UBSAN reports citing cpia1.c:1031 or shift exponent too large; review dmesg and audit logs for USB device attach events involving gspca/cpia1 immediately preceding crashes.

What your security team should do

• Apply the referenced upstream commit or newer stable kernel branch immediately on affected systems
• Disable or blacklist the cpia1 module if the hardware is not required
• Monitor for kernel oops or UBSAN reports involving cpia1.c