Executive Summary

CVE-2026-56208 is a heap buffer overflow vulnerability found in libaom, the reference AV1 codec implementation. The flaw occurs in the AV1 encoder's Look-Ahead Processing (LAP) mode when the parameter g_lag_in_frames is set to 1 or higher. In this mode, the first-pass stats ring buffer wrap-around guard is bypassed, causing a 232-byte out-of-bounds write on every encoded frame after the second. This overflow corrupts adjacent heap objects and their metadata.

The vulnerability arises because the wrap-around guard only activates during the first pass, but LAP mode runs as a one-pass process, so the buffer pointer never wraps correctly. This leads to memory corruption and can cause process crashes or potentially allow code execution if exploited.

An attacker who can influence encoder configuration in environments like transcoding services or WebRTC sessions could exploit this vulnerability.

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Mitigation Strategies

The primary mitigation step is to upgrade libaom to version 3.14.0 or later, where the vulnerability has been fixed by properly handling the buffer pointer in LAP mode to prevent overflow.

If upgrading immediately is not possible, consider restricting or sanitizing input that controls the encoder configuration, especially the g_lag_in_frames parameter, to prevent untrusted users from enabling LAP mode.

Monitoring and limiting access to services that expose libaom encoding configuration to untrusted input, such as transcoding services or WebRTC sessions, can reduce the risk of exploitation.

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Impact Analysis

This vulnerability can lead to denial of service by causing the process using the AV1 encoder to crash due to heap corruption.

More severely, it may allow an attacker to execute arbitrary code if they can control the encoder configuration, potentially compromising the security of the system running the vulnerable libaom version.

Systems that use libaom for encoding AV1 video streams, such as transcoding services or WebRTC-enabled browsers, are at risk if they expose encoder configuration to untrusted input.

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Detection Guidance

This vulnerability occurs in libaom versions v2.0.0 through v3.13.3 when the AV1 encoder is configured with g_lag_in_frames set to 1 or higher, enabling Look-Ahead Processing (LAP) mode. Detection involves identifying if your system or application uses a vulnerable libaom version and if the encoder configuration allows untrusted input to set g_lag_in_frames.

Since the vulnerability causes a heap buffer overflow leading to process crashes or potential code execution, monitoring for crashes or abnormal behavior in applications using libaom for AV1 encoding (such as transcoding services or WebRTC sessions) can help detect exploitation attempts.

Specific commands to detect the vulnerability are not provided in the available resources. However, you can check the installed libaom version with commands like:

• dpkg -l | grep libaom (on Debian/Ubuntu systems)
• rpm -qa | grep libaom (on Red Hat/CentOS systems)

Additionally, inspecting application logs for crashes related to AV1 encoding or using debugging tools to monitor heap corruption in processes using libaom may help detect exploitation.

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Compliance Impact

The provided information does not specify any direct impact of this vulnerability on compliance with common standards and regulations such as GDPR or HIPAA.

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