CVE-2021-39648

What it actually does

Race condition in gadget_dev_desc_UDC_show of configfs.c allows local disclosure of kernel heap memory contents when System execution privileges are held.

Why it matters to the business

Privileged local processes could read kernel memory that may contain sensitive data, increasing risk of information leakage on Android devices; the issue is old with low exploitation probability and no known active campaigns.

How an attack unfolds

An attacker with System privileges triggers the race condition in the USB gadget configfs handling code to read uninitialized kernel heap memory; no user interaction or network access is required, and the low EPSS plus absence from KEV indicate limited observed exploitation despite mentions of generic kernel race and privilege escalation themes.

How to fix it

Apply upstream Linux kernel patches addressing the configfs race condition and update to a patched Android kernel build; monitor vendor security bulletins for device-specific updates since no fixed versions are listed.

How to confirm the fix worked

Verify kernel source no longer contains the vulnerable gadget_dev_desc_UDC_show implementation, run concurrency stress tests on USB gadget configuration paths, and confirm memory disclosure is no longer possible under System privileges.

Typical attack path

1. Obtain System execution privileges on the target Android device
2. Trigger concurrent access to gadget_dev_desc_UDC_show in configfs.c
3. Read disclosed kernel heap memory contents

How to detect it

Examine kernel logs and audit records for unusual concurrent access patterns around configfs USB gadget operations; look for processes running with System privileges attempting to read from gadget device descriptors.

What your security team should do

• Prioritize patching Android devices that expose USB gadget functionality
• Review device update policies to ensure kernel patches are applied promptly
• Monitor EPSS trend and upstream Linux kernel advisories for any increase in activity