CVE-2021-39714

What it actually does

Integer overflow in ion_buffer_kmap_get of ion.c triggers a use-after-free condition in the Android kernel ION memory allocator, enabling an attacker to corrupt kernel memory structures and achieve arbitrary code execution.

Why it matters to the business

Local attackers can obtain full root privileges on affected Android devices, allowing complete device compromise, data theft, persistence, and bypassing of all application sandbox protections.

How an attack unfolds

An attacker with local code execution on the device supplies crafted parameters to ion_buffer_kmap_get that cause an integer overflow during buffer mapping; the resulting use-after-free is then leveraged to overwrite kernel function pointers or data structures, escalating privileges to root without user interaction.

How to fix it

Apply the upstream kernel patch referenced by Android ID A-205573273 and update to a patched Android kernel build that corrects the integer overflow and use-after-free in ion.c.

How to confirm the fix worked

Verify that devices are running a kernel build containing the fix for A-205573273; confirm absence of the vulnerable ion_buffer_kmap_get implementation via source inspection or binary diffing against patched kernels.

Typical attack path

1. Obtain local code execution via a malicious application or compromised process
2. Invoke ion_buffer_kmap_get with values that trigger the integer overflow
3. Trigger the resulting use-after-free to corrupt kernel memory
4. Hijack control flow or data structures to execute arbitrary code at kernel level
5. Install persistent root-level malware or exfiltrate data

How to detect it

Review system and kernel logs for anomalous ION buffer allocation or mapping failures around the time of suspected compromise; examine for unexpected privilege changes or new root processes following local app activity.

What your security team should do

• Prioritize deployment of patched Android kernel images to all managed devices
• Enforce application allow-listing and restrict local code execution surfaces where possible
• Monitor vendor security bulletins for downstream device updates that incorporate the fix