CVE-2021-39657

What it actually does

Out-of-bounds read in ufshcd_eh_device_reset_handler of ufshcd.c caused by missing bounds check, allowing disclosure of kernel memory contents to a local attacker with system privileges.

Why it matters to the business

Risk of sensitive kernel memory exposure on Android devices, potentially compromising confidential data in environments where system-level access is obtained.

How an attack unfolds

An attacker who has already obtained system execution privileges triggers the UFS host controller device reset handler to perform an unchecked memory read and exfiltrate kernel data; no user interaction is required.

How to fix it

Apply upstream Linux kernel patches that add the missing bounds check in ufshcd.c; track Android security bulletins for device-specific kernel updates as no fixed versions are published for the affected Android kernels.

How to confirm the fix worked

Inspect the ufshcd.c source for the addition of bounds validation inside ufshcd_eh_device_reset_handler and confirm the updated kernel is running on test devices.

Typical attack path

1. Gain system execution privileges on the Android device
2. Trigger or invoke ufshcd_eh_device_reset_handler
3. Read kernel memory beyond allocated bounds

How to detect it

Review system and kernel logs for invocations of the UFS reset handler combined with subsequent anomalous memory access or information disclosure events; examine memory forensics for unexpected data reads from the driver.

What your security team should do

• Expedite deployment of patched Android kernels across the fleet
• Limit grant of system execution privileges to only essential processes
• Incorporate kernel version checks into device compliance scans