CVE-2024-35367

What it actually does

Out-of-bounds read in the VP8 subpel filter implementation within libavcodec/ppc/vp8dsp_altivec.c caused by an undersized static vec_s8 array accessed during Altivec-optimized decoding on PowerPC.

Why it matters to the business

Media processing pipelines on PowerPC systems may experience crashes or limited memory disclosure when handling certain VP8 video content, potentially disrupting video workflows and requiring emergency patching of widely deployed FFmpeg instances.

How an attack unfolds

An attacker crafts a VP8 video stream whose subpel filter coefficients trigger an out-of-bounds read in the Altivec-optimized h_subpel_filters_outer array; the malicious file is then supplied to any application that uses the affected FFmpeg decoder on PowerPC hardware.

How to fix it

Upgrade FFmpeg to the commit 09e6840cf7a3ee07a73c3ae88a020bf27ca1a667 or later; rebuild any dependent packages and redeploy the updated binaries across all PowerPC environments.

How to confirm the fix worked

Confirm the installed FFmpeg git revision contains commit 09e6840cf7a3ee07a73c3ae88a020bf27ca1a667; run regression tests with VP8 content exercising subpel filters on PowerPC hardware and verify absence of crashes or sanitizer reports.

Typical attack path

1. Identify or create a VP8 bitstream that indexes beyond the declared h_subpel_filters_outer array bounds
2. Embed the crafted stream inside a container accepted by the target application
3. Deliver the file via web download, email attachment, or media ingestion pipeline
4. Trigger decoding on a PowerPC system using an unpatched FFmpeg build
5. Observe crash or harvest leaked memory contents from the out-of-bounds read

How to detect it

Review application and system logs for segmentation faults or out-of-bounds access errors during VP8 decoding on PowerPC; correlate with file ingestion timestamps and inspect any core dumps or sanitizer output for references to vp8dsp_altivec.c.

What your security team should do

• Prioritize patching all PowerPC FFmpeg deployments within the next maintenance window
• Inventory downstream applications and libraries that statically link or bundle FFmpeg
• Add VP8 decoding test cases that target Altivec code paths to CI pipelines
• Monitor EPSS and exploit maturity signals for any future increase in risk