CVE-2026-56210: libaom AV1 Buffer Overflow Vulnerability

CVE-2026-56210 Overview

CVE-2026-56210 is an out-of-bounds heap read vulnerability in libaom, the reference implementation of the AV1 video codec maintained by the Alliance for Open Media. The flaw resides in the Scalable Video Coding (SVC) layer ID control function. A missing bounds check allows callers to set a spatial_layer_id value that exceeds the configured number of layers. When the encoder computes a layer context array index, it reads approximately 40,728 bytes outside the allocated heap buffer. The issue is classified as [CWE-125] Out-of-Bounds Read.

Critical Impact
Attackers who can influence SVC encoder parameters in a network-facing service can leak heap memory contents or crash the process through a segmentation fault.

Affected Products

libaom reference AV1 codec implementation (AOMedia)
Downstream applications and services that link libaom and expose SVC encoder controls
Red Hat distributions tracking the upstream advisory

Discovery Timeline

2026-06-19 - CVE-2026-56210 published to the National Vulnerability Database
2026-06-22 - Last updated in NVD database

Technical Details for CVE-2026-56210

Vulnerability Analysis

The vulnerability exists in the SVC layer ID control path within libaom. SVC enables encoders to produce a bitstream with multiple spatial and temporal layers, where each layer is tracked by a context structure stored in a fixed-size array. The control function that assigns a spatial_layer_id does not validate the supplied value against the number of layers the encoder was configured for.

When the encoder later uses the unchecked spatial_layer_id to compute an index into the layer context array, it dereferences memory far beyond the buffer boundary. The read spans roughly 40,728 bytes of adjacent heap memory. Depending on heap layout, the operation either returns sensitive in-process data to the attacker or hits an unmapped page, terminating the process with a segmentation fault.

Root Cause

The root cause is a missing bounds check in the SVC layer ID control function. The code accepts any caller-supplied spatial_layer_id and uses it directly as an array offset without comparing it to the configured layer count. The upstream fix is tracked in the AOM source tree under commit a93ba0ffaa. See the AOM Git Commit Change for the patch.

Attack Vector

Exploitation requires the attacker to influence SVC encoder configuration parameters supplied to a service that uses libaom. This is feasible in network-facing transcoders, real-time communication servers, browser-exposed encoding APIs, and media processing pipelines that pass user-controlled SVC settings into the encoder. User interaction is required, consistent with scenarios where a victim renders or transmits attacker-crafted media. Successful exploitation yields information disclosure of heap contents or a denial-of-service crash. The vulnerability does not, on its own, permit code execution or integrity modification.

No public exploit, proof-of-concept, or in-the-wild activity has been reported. The vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog.

Detection Methods for CVE-2026-56210

Indicators of Compromise

Repeated segmentation faults or SIGSEGV crashes in processes linking libaom, particularly during SVC encoder initialization
AddressSanitizer reports of heap-buffer-overflow reads near layer context array accesses
Anomalous SVC configuration payloads supplied to media services where spatial_layer_id exceeds the configured layer count

Detection Strategies

Inspect crash dumps and core files from media services for faults inside libaom SVC layer control routines
Run fuzzing or ASan-instrumented builds against media ingestion endpoints to surface out-of-bounds reads
Audit application logs for malformed SVC parameter sets that originate from untrusted clients

Monitoring Recommendations

Track process restart counts and crash frequency for transcoders, WebRTC gateways, and browser media subprocesses
Alert on outbound responses that contain unexpectedly large or unstructured byte ranges from media endpoints, which may indicate leaked heap data
Maintain version inventory for libaom across container images and host packages to identify unpatched systems

How to Mitigate CVE-2026-56210

Immediate Actions Required

Update libaom to the version that includes upstream commit a93ba0ffaa once distributed by your operating system vendor
Rebuild and redeploy applications statically linked against vulnerable libaom releases
Restrict SVC encoder parameter inputs to trusted callers until patches are applied

Patch Information

The upstream fix adds bounds validation for spatial_layer_id against the configured number of layers. Apply vendor-supplied package updates as they become available. Reference the Red Hat CVE Advisory, Red Hat Bug Report 2490801, and the Chromium Issue Tracker Entry for distribution and browser-specific tracking.

Workarounds

Validate and clamp spatial_layer_id values at the application layer before passing them to libaom
Disable SVC encoding features in services that do not require multi-layer output
Isolate media encoding workloads in sandboxed processes or containers to limit the impact of heap memory disclosure or process crashes

bash

# Configuration example: verify installed libaom version on Red Hat-based systems
rpm -q libaom
# After patch availability, update via the distribution package manager
sudo dnf update libaom