CVE-2026-56208
Description
A heap buffer overflow vulnerability was found in libaom, the reference AV1 codec implementation. A flaw in the AV1 encoder's Look-Ahead Processing (LAP) mode causes the first-pass stats ring buffer wrap-around guard to be bypassed when g_lag_in_frames is set to 1 or higher. This results in a 232-byte out-of-bounds write on every encoded frame after the second, corrupting adjacent heap objects. An attacker who can influence encoder configuration in a transcoding service or WebRTC session could exploit this to cause a denial of service (process crash) or potentially achieve code execution.
Statement
This vulnerability is rated as Important severity because a heap buffer overflow with attacker-influenced data can cause reliable denial of service and potentially lead to code execution, though the attacker has only indirect control over the written values (encoder-computed statistics). In Red Hat products, libaom ships bundled within Firefox and Thunderbird as a statically-linked dependency used for AV1 decoding and WebRTC encoding. The vulnerable code path requires the encoder to be configured with g_lag_in_frames >= 1 (Look-Ahead Processing mode). In Firefox's WebRTC implementation, the encoder configuration is controlled by the browser itself and not exposed to remote peers, which significantly limits the attack surface compared to standalone transcoding services. RHEL-AI 3.4 and Hummingbird 1 ship standalone libaom (aom) packages at versions within the affected range. Applications on those platforms that use the libaom encoder API with LAP mode and accept untrusted configuration input are vulnerable.
Mitigation
There is no complete mitigation for this vulnerability. The following measures can reduce risk:
1. If using libaom as a standalone encoder library, avoid setting g_lag_in_frames to values >= 1 when processing untrusted input, or validate all encoder configuration parameters before passing them to the libaom API.
2. For Firefox and Thunderbird, ensure browsers are updated to versions that include the patched libaom (v3.14.0 or later).
3. For standalone libaom deployments (RHEL-AI, Hummingbird), restrict access to the encoding service to trusted clients only.
4. Apply network-level access controls to limit who can submit video for encoding.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 7.6 | N/A | 7.6 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | None | N/A | None |
| User Interaction | Required | N/A | Required |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | Low | N/A | Low |
| Integrity Impact | Low | N/A | Low |
| Availability Impact | High | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:H
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:H
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Crash, Exit, or Restart; DoS: Resource Consumption (CPU); DoS: Resource Consumption (Memory)
Buffer overflows generally lead to crashes. Other attacks leading to lack of availability are possible, including putting the program into an infinite loop.
Integrity,Confidentiality,Availability,Access Control
Technical Impact: Execute Unauthorized Code or Commands; Bypass Protection Mechanism; Modify Memory
Buffer overflows often can be used to execute arbitrary code, which is usually outside the scope of a program's implicit security policy. Besides important user data, heap-based overflows can be used to overwrite function pointers that may be living in memory, pointing it to the attacker's code. Even in applications that do not explicitly use function pointers, the run-time will usually leave many in memory. For example, object methods in C++ are generally implemented using function pointers. Even in C programs, there is often a global offset table used by the underlying runtime.
Integrity,Confidentiality,Availability,Access Control,Other
Technical Impact: Execute Unauthorized Code or Commands; Bypass Protection Mechanism; Other
When the consequence is arbitrary code execution, this can often be used to subvert any other security service.
Acknowledgements
Red Hat would like to thank The FuzzAnything Team (FuzzAnything) for reporting this issue.
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