CVE-2021-39800

What it actually does

Use-after-free in ion_ioctl allows reading kernel heap memory contents after deallocation, enabling local disclosure of sensitive kernel data.

Why it matters to the business

Local attackers on affected Android devices can extract kernel information that may assist further attacks or expose internal system details, increasing risk on unpatched devices still in use.

How an attack unfolds

An attacker with local access issues crafted ioctl operations against the ION driver to trigger the use-after-free and read residual kernel heap data without requiring elevated privileges or user interaction.

How to fix it

Apply Android kernel patches addressing A-208277166; upgrade to a maintained kernel release that eliminates the use-after-free in ion-ioctl.c.

How to confirm the fix worked

Review kernel source for upstream fixes in ion-ioctl.c, confirm absence of the vulnerable code path, and test that ioctl operations no longer expose freed memory.

Typical attack path

1. Gain local user access on an Android device
2. Open /dev/ion and issue malicious ioctl calls
3. Trigger the use-after-free condition in ion_ioctl
4. Read and parse leaked kernel heap contents for sensitive data

How to detect it

Monitor system logs and audit trails for repeated or anomalous ioctl activity targeting the ION driver; examine crash dumps or memory leak reports referencing ion-ioctl.c.

What your security team should do

• Prioritize patching Android devices with the latest kernel security updates
• Limit local untrusted code execution on high-value devices
• Audit custom kernels for backported fixes to ion memory handling