CVE-2024-49970

What it actually does

Out-of-bounds array access in dcn401_stream_encoder_create when eng_id reaches 5 against a four-element stream_enc_regs array, resulting in buffer overflow and undefined behavior in the AMD display driver.

Why it matters to the business

Systems using affected AMD DCN401 hardware may experience kernel instability, crashes, or potential local privilege escalation; urgency remains low given absence from known exploitation lists and modest exploit probability, though Linux kernel prevalence amplifies patch priority across distributions.

How an attack unfolds

An attacker with local access crafts conditions to invoke stream encoder creation passing an out-of-bounds eng_id of 5, triggering the missing bounds check and overflowing the registers array; listed threat actor campaigns targeting Linux kernel out-of-bounds issues illustrate possible paths but no confirmed active exploitation exists for this specific flaw.

How to fix it

Update the Linux kernel to a version containing commit b219b46ad42df1dea9258788bcfea37181f3ccb2 or later; for Rocky Linux 8 packages such as thunderbird apply the fixed build 78.11.0-1.el8_4 or equivalent distribution kernel update that backports the bounds check.

How to confirm the fix worked

Confirm the patched kernel version is running, verify the dcn401_resource.c file contains the added bounds check before array access, and test stream encoder creation under normal display workloads without triggering the prior overflow condition.

Typical attack path

1. Obtain local code execution or user context on a vulnerable Linux system with DCN401 hardware
2. Trigger display resource initialization paths that call dcn401_stream_encoder_create with eng_id=5
3. Cause out-of-bounds memory access and subsequent undefined behavior for crash or escalation

How to detect it

Examine kernel logs and dmesg output around display initialization for buffer overflow warnings or smatch-style errors referencing stream_enc_regs; review audit logs for unusual display resource allocation attempts by local processes on AMD hardware.

What your security team should do

• Prioritize kernel updates on all AMD DCN401 systems within standard change windows
• Monitor upstream stable kernel releases for additional backports
• Review local display driver initialization logs for any prior unexplained crashes that could indicate attempted triggering