CVE-2026-56210
Description
A heap-buffer-overflow read 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 setting a spatial_layer_id exceeding the configured number of layers. This causes an out-of-bounds heap read of approximately 40,728 bytes when computing a layer context array index. An attacker who can influence SVC encoder parameters in a network-facing service could exploit this for information disclosure (heap content leak) or denial of service (segmentation fault from hitting unmapped memory).
Statement
This vulnerability is rated as Important severity because the 40KB out-of-bounds heap read can disclose sensitive information from adjacent heap allocations (including pointers useful for ASLR bypass in chained attacks) and reliably causes denial of service by hitting unmapped pages. In Red Hat products, libaom ships bundled within Firefox and Thunderbird. The vulnerable code path requires the SVC encoder feature to be enabled and an attacker to set spatial_layer_id to a value exceeding the number of configured spatial layers. In Firefox's WebRTC implementation, SVC layer parameters are managed internally by the browser and not directly exposed to remote peers, which limits exploitability. 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 that expose SVC encoder layer configuration to untrusted input are affected.
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 does not exceed the number of configured spatial layers before calling aom_codec_control with AV1E_SET_SVC_LAYER_ID.
2. Restrict access to encoding services to trusted clients only.
3. For Firefox and Thunderbird, ensure browsers are updated to versions that include the patched libaom (v3.14.0 or later).
4. Monitor encoding service processes for unexpected crashes (segfaults) that may indicate exploitation attempts.
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 | Low | N/A | Low |
| Integrity Impact | None | N/A | None |
| 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:N/A:H
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:H
Understanding the Weakness (CWE)
Confidentiality
Technical Impact: Read Memory
An attacker could get secret values such as cryptographic keys, PII, memory addresses, or other information that could be used in additional attacks.
Confidentiality
Technical Impact: Bypass Protection Mechanism
Out-of-bounds memory could contain memory addresses or other information that can be used to bypass ASLR and other protection mechanisms in order to improve the reliability of exploiting a separate weakness for code execution.
Availability
Technical Impact: DoS: Crash, Exit, or Restart
An attacker could cause a segmentation fault or crash by causing memory to be read outside of the bounds of the buffer. This is especially likely when the code reads a variable amount of data and assumes that a sentinel exists to stop the read operation, such as a NUL in a string.
Other
Technical Impact: Varies by Context
The read operation could produce other undefined or unexpected results.
Acknowledgements
Red Hat would like to thank The FuzzAnything Team (FuzzAnything) for reporting this issue.
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