High [CVE-2026-56209] arbitrary address write via SVC layer context OOB and cyclic refresh map pointer hijack
This high-severity Red Hat Linux advisory covers CVE-2026-56209 affecting Red Hat Enterprise Linux AI 3.5 for RHEL 9, Red Hat Hardened Images, Red Hat AI Inference Server.
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Summary
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. 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.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative — check it before change work.
Official advisory · high-confidence parse· fetched 16 days ago·verify at source
- aom-0:3.14.0-1.el9ai
- aom-main-3.14.0-0.1.hum1
- RHSA-2026:42875
- RHSA-2026:30814
Official advisory · high-confidence parse· fetched 16 days ago·verify at source
Mitigation checklist
- 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.
Official advisory · high-confidence parse· fetched 16 days ago·verify at source
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