CVE-2026-56209
Description
An arbitrary address write vulnerability was found in libaom, the reference AV1 codec implementation. A missing bounds check in the SVC (Scalable Video Coding) layer ID control function allows an attacker to inject an arbitrary pointer into the cyclic refresh map field via crafted image pixel values. The encoder then writes approximately 1,200 bytes at the attacker-controlled address. This is fully deterministic and does not require a separate information leak. An attacker who can supply frames to a network-facing libaom encoder with SVC enabled could exploit this for denial of service or potential code execution.
Statement
This vulnerability is rated as Critical severity because it provides a fully deterministic arbitrary address write primitive that requires no information leak and is self-bootstrapping from attacker-controlled pixel values. The 1,200-byte write at an attacker-chosen address is sufficient for control flow hijacking. In Red Hat products, libaom ships bundled within Firefox and Thunderbird. The vulnerable code path requires the SVC (Scalable Video Coding) encoder feature to be enabled and the attacker to control both the layer_id configuration and the image frame pixel values. In Firefox's WebRTC implementation, SVC encoding parameters and frame submission are managed internally by the browser; a remote peer cannot directly set arbitrary layer IDs or inject pixel values into the local encoder. This significantly reduces exploitability in the browser context. RHEL-AI 3.4 (aom 3.12.0) and Hummingbird 1 (aom 3.13.3) ship standalone libaom packages within the affected version range. Services on those platforms that expose the SVC encoder API with attacker-controlled layer configuration and frame input are at highest risk.
Mitigation
There is no complete mitigation for this vulnerability. The following measures can reduce risk:
1. If using libaom as a standalone encoder library with SVC enabled, validate that spatial_layer_id and temporal_layer_id values are within the configured range [0, configured_layers) before calling aom_codec_control with AV1E_SET_SVC_LAYER_ID.
2. Restrict access to encoding services to trusted clients only. Do not expose libaom SVC encoder configuration to untrusted input.
3. For Firefox and Thunderbird, ensure browsers are updated to versions that include the patched libaom (v3.14.0 or later).
4. Deploy encoding services with ASLR, stack canaries, and other exploit mitigation technologies enabled.
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 | 7.1 | N/A | 7.1 |
| 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 | None | N/A | None |
| 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:N/I:L/A:H
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:H
Understanding the Weakness (CWE)
Integrity
Technical Impact: Modify Memory; Execute Unauthorized Code or Commands
Write operations could cause memory corruption. In some cases, an adversary can modify control data such as return addresses in order to execute unexpected code.
Availability
Technical Impact: DoS: Crash, Exit, or Restart
Attempting to access out-of-range, invalid, or unauthorized memory could cause the product to crash.
Other
Technical Impact: Unexpected State
Subsequent write operations can produce undefined or unexpected results.
Acknowledgements
Red Hat would like to thank The FuzzAnything Team (FuzzAnything) for reporting this issue.
Frequently Asked Questions
Not sure what something means? Check out our Security Glossary.
Want to get errata notifications? Sign up here.
