CVE-2026-30997: FFmpeg AV1 Decoder DoS Vulnerability

CVE-2026-30997 Overview

An out-of-bounds read vulnerability has been identified in the read_global_param() function within libavcodec/av1dec.c of FFmpeg v8.0.1. This memory safety issue allows remote attackers to cause a Denial of Service (DoS) condition by supplying specially crafted media input to the affected AV1 decoder component.

Critical Impact

Remote attackers can crash FFmpeg-based applications by providing malicious AV1 video content, potentially disrupting media processing services and streaming infrastructure.

Affected Products

• FFmpeg v8.0.1
• Applications and services utilizing FFmpeg's AV1 decoding functionality
• Media processing pipelines incorporating vulnerable FFmpeg versions

Discovery Timeline

• 2026-04-13 - CVE CVE-2026-30997 published to NVD
• 2026-04-13 - Last updated in NVD database

Technical Details for CVE-2026-30997

Vulnerability Analysis

This vulnerability is classified as CWE-125 (Out-of-Bounds Read), a memory corruption issue that occurs when the application reads data beyond the boundaries of an allocated memory buffer. In FFmpeg's AV1 decoder implementation, the read_global_param() function fails to properly validate input boundaries when parsing global motion parameters from AV1 bitstreams.

When processing a maliciously crafted AV1 video file, the decoder attempts to read memory locations outside the intended buffer region. While this specific vulnerability results in a Denial of Service rather than code execution, out-of-bounds read vulnerabilities can potentially leak sensitive memory contents in certain contexts.

The network attack vector makes this particularly concerning for server-side media processing applications, transcoding services, and web applications that accept user-uploaded video content for processing.

Root Cause

The root cause lies in insufficient bounds checking within the read_global_param() function in libavcodec/av1dec.c. When parsing global motion parameters from AV1 frame headers, the function does not adequately validate that the requested read operations remain within the allocated buffer boundaries. An attacker can craft an AV1 bitstream with malformed global motion parameter data that triggers reads beyond the buffer limits.

Attack Vector

The vulnerability is exploitable over the network without requiring authentication or user interaction. An attacker can deliver the malicious payload through various means:

1. Uploading a crafted AV1 video file to a media processing service
2. Embedding malicious AV1 content in a web page that triggers server-side processing
3. Submitting crafted media through streaming protocols to FFmpeg-based transcoders
4. Distributing malicious media files through file sharing or content delivery systems

The attack succeeds when FFmpeg attempts to decode the malformed AV1 content, causing the out-of-bounds read to trigger a crash or undefined behavior in the application.

The vulnerability manifests in the AV1 global motion parameter parsing logic within the decoder. Detailed technical analysis is available in the CVE-2026-30997 Analysis documentation. The FFmpeg source repository contains the affected libavcodec/av1dec.c file.

Detection Methods for CVE-2026-30997

Indicators of Compromise

• Unexpected crashes or segmentation faults in FFmpeg processes during AV1 video processing
• Application logs showing memory access violations in libavcodec components
• Abnormal termination of media transcoding or streaming services
• Core dumps indicating out-of-bounds access in av1dec.c related functions

Detection Strategies

• Monitor FFmpeg process stability and implement crash detection for media processing services
• Deploy application-level monitoring to detect repeated FFmpeg worker restarts
• Implement input validation to identify potentially malformed AV1 bitstreams before processing
• Use AddressSanitizer (ASan) in development and staging environments to detect memory access violations

Monitoring Recommendations

• Enable detailed logging for FFmpeg operations to capture error conditions before crashes
• Implement health checks for media processing services with automatic alerting on availability degradation
• Monitor system resource utilization for abnormal patterns that may indicate exploitation attempts
• Track file upload patterns and flag unusual volumes of AV1 video submissions

How to Mitigate CVE-2026-30997

Immediate Actions Required

• Inventory all systems and applications using FFmpeg to identify vulnerable deployments
• Prioritize patching for internet-facing media processing services
• Consider temporarily disabling AV1 decoding functionality if not business-critical
• Implement input sanitization to reject or quarantine suspicious media files pending analysis

Patch Information

Organizations should monitor the FFmpeg project repository for security patches addressing this vulnerability. Review the detailed vulnerability analysis for additional technical guidance. Apply vendor-supplied patches as soon as they become available, following standard change management procedures.

Workarounds

• Disable AV1 codec support in FFmpeg configurations where this format is not required
• Implement process isolation and sandboxing for media processing workloads to limit crash impact
• Deploy rate limiting on media upload endpoints to slow potential exploitation attempts
• Use containerized FFmpeg deployments with automatic restart policies to maintain service availability

# Example: Disable AV1 decoder in FFmpeg build configuration
./configure --disable-decoder=av1

# Example: Run FFmpeg in restricted sandbox (Linux)
firejail --noprofile --quiet ffmpeg -i input.mp4 output.mp4