Linux Distros Unpatched Vulnerability : CVE-2026-56211

critical Nessus Plugin ID 321806

Synopsis

The Linux/Unix host has one or more packages installed with a vulnerability that the vendor indicates will not be patched.

Description

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

- A remote code execution vulnerability was found in libaom, the reference AV1 codec implementation.
Insufficient bounds validation in the AV1 encoder's SVC (Scalable Video Coding) layer ID control allows an attacker to supply crafted video frame pixels that overlap with internal encoder layer context structures.
In fork-based video processing services, an attacker can use this to hijack the cyclic refresh map pointer, brute-force the process base address via a crash oracle, and redirect control flow to achieve arbitrary command execution. Exploitation requires the target service to use libaom with SVC encoding enabled and accept attacker-supplied video frames. (CVE-2026-56211)

Note that Nessus relies on the presence of the package as reported by the vendor.

Solution

There is no known solution at this time.

Plugin Details

Severity: Critical

ID: 321806

File Name: unpatched_CVE_2026_56211.nasl

Version: 1.1

Type: Local

Agent: unix

Family: Misc.

Published: 6/20/2026

Updated: 6/20/2026

Supported Sensors: Nessus Agent, Nessus

Risk Information

VPR

Risk Factor: High

Score: 8.0

CVSS v2

Risk Factor: High

Base Score: 7.5

Temporal Score: 6.4

Vector: CVSS2#AV:N/AC:L/Au:N/C:P/I:P/A:P

CVSS Score Source: CVE-2026-56211

CVSS v3

Risk Factor: Critical

Base Score: 9.8

Temporal Score: 9

Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Temporal Vector: CVSS:3.0/E:U/RL:U/RC:C

Vulnerability Information

CPE: cpe:/o:redhat:enterprise_linux:9, p-cpe:/a:redhat:enterprise_linux:thunderbird, p-cpe:/a:redhat:enterprise_linux:firefox, p-cpe:/a:redhat:enterprise_linux:firefox-x11, cpe:/o:redhat:enterprise_linux:10

Required KB Items: Host/cpu, Host/local_checks_enabled, global_settings/vendor_unpatched, Host/OS/identifier

Exploit Ease: No known exploits are available

Vulnerability Publication Date: 6/19/2026

Reference Information

CVE: CVE-2026-56211

Detections

Analytics