CVE-2021-47347

What it actually does

The vulnerability is a buffer overflow in the Linux kernel wl1251 wireless driver where wl1251_cmd_scan performs an unchecked memcpy that can exceed the maximum allowed buffer size.

Why it matters to the business

Systems using the wl1251 chipset may experience kernel crashes or allow local privilege escalation, disrupting wireless networking and potentially enabling deeper system compromise on affected Linux deployments.

How an attack unfolds

An attacker supplies a crafted scan command structure containing data larger than the expected maximum to wl1251_cmd_scan, causing the memcpy to write past the end of the destination buffer and corrupt adjacent kernel memory.

How to fix it

Apply the upstream kernel commit that adds an explicit length validation check before the memcpy call in wl1251_cmd_scan; rebuild and deploy the patched kernel on affected systems.

How to confirm the fix worked

Inspect the wl1251_cmd_scan source for the added length guard or confirm the running kernel contains the fix by comparing against the resolved commit; test scan functionality with oversized inputs to verify rejection.

Typical attack path

1. Locate a Linux system exposing the wl1251 driver interface
2. Craft a malicious command buffer exceeding the maximum scan size
3. Invoke wl1251_cmd_scan with the oversized payload
4. Trigger memcpy overflow to corrupt kernel memory for code execution or denial of service

How to detect it

Review kernel logs and dmesg output for wl1251 driver crashes or memory corruption warnings around scan command handling; correlate with processes invoking wireless scan operations.

What your security team should do

• Prioritize patching all kernels that include the vulnerable wl1251 driver code
• Restrict untrusted local access to wireless driver interfaces until updated
• Monitor kernel logs for wl1251-related oops or memory corruption events