Amazon Linux 2 : microcode_ctl, --advisory ALAS2-2026-3872 (ALAS-2026-3872)

high Nessus Plugin ID 341906

Synopsis

The remote Amazon Linux 2 host is missing a security update.

Description

The version of microcode_ctl installed on the remote host is prior to 2.1-47. It is, therefore, affected by multiple vulnerabilities as referenced in the ALAS2-2026-3872 advisory.

Improper handling of overlap between protected memory ranges for some Intel(R) Xeon(R) 6 processors when using Intel(R) TDX within SMM may allow an escalation of privilege. SMM adversary with a privileged user combined with a high complexity attack may enable escalation of privilege. This result may potentially occur via local access when attack requirements are present with special internal knowledge and requires no user interaction. The potential vulnerability may impact the confidentiality (high), integrity (high) and availability (none) of the vulnerable system, resulting in subsequent system confidentiality (none), integrity (none) and availability (none) impacts. (CVE-2025-31936)

Insufficient granularity of access control in some subsystem for some Intel(R) Xeon(R) 6 Scalable processors with Intel(R) TDX may allow an information disclosure. Authorized adversary with an authenticated user combined with a high complexity attack may enable data exposure. This result may potentially occur via local access when attack requirements are present with special internal knowledge and requires no user interaction. The potential vulnerability may impact the confidentiality (none), integrity (none) and availability (none) of the vulnerable system, resulting in subsequent system confidentiality (high), integrity (none) and availability (none) impacts. (CVE-2025-31938)

Improper handling of values for some Intel(R) Processors within Ring 0: Kernel, Hypervisor and Bare Metal OS may allow an escalation of privilege. Authorized adversary with a privileged user combined with a high complexity attack may enable escalation of privilege. This result may potentially occur via local access when attack requirements are present with special internal knowledge and require no user interaction. The potential vulnerability may impact the confidentiality (low), integrity (low) and availability (none) of the vulnerable system, resulting in subsequent system confidentiality (high), integrity (high) and availability (none) impacts. (CVE-2025-35973)

Hardware logic contains race conditions for some 3rd Gen Intel(R) Xeon(R) Scalable Processors within Ring 3: unprivileged software may allow a denial of service. Unprivileged software adversary with an authenticated user combined with a high complexity attack may enable denial of service. This result may potentially occur via local access when attack requirements are not present with special internal knowledge and requires no user interaction. The potential vulnerability may impact the confidentiality (none), integrity (none) and availability (high) of the vulnerable system, resulting in subsequent system confidentiality (none), integrity (none) and availability (high) impacts. (CVE-2026-20707)

Always-incorrect control flow implementation in some firmware for some Intel(R) Xeon(R) processors may allow an escalation of privilege. System software adversary with a privileged user combined with a high complexity attack may enable escalation of privilege. This result may potentially occur via local access when attack requirements are not present without special internal knowledge and requires no user interaction. The potential vulnerability may impact the confidentiality (none), integrity (none) and availability (none) of the vulnerable system, resulting in subsequent system confidentiality (high), integrity (high) and availability (none) impacts. (CVE-2026-20713)

Improper access control for some Intel(R) Processors within Ring 3: User Applications may allow an escalation of privilege. Simple hardware adversary with an authenticated user combined with a high complexity attack may enable escalation of privilege. This result may potentially occur via local access when attack requirements are present with special internal knowledge and requires no user interaction. The potential vulnerability may impact the confidentiality (high), integrity (high) and availability (none) of the vulnerable system, resulting in subsequent system confidentiality (none), integrity (none) and availability (none) impacts. (CVE-2026-20716)

Improper input validation for some Intel(R) Xeon(R) processors within firmware may allow an escalation of privilege. Startup code and smm adversary with a privileged user combined with a high complexity attack may enable data alteration. This result may potentially occur via local access when attack requirements are present without special internal knowledge and requires no user interaction. The potential vulnerability may impact the confidentiality (none), integrity (none) and availability (none) of the vulnerable system, resulting in subsequent system confidentiality (none), integrity (high) and availability (none) impacts. (CVE-2026-20901)

Exposure of sensitive information caused by incorrect data forwarding during transient execution for some Intel(R) Processors within Ring 0: Hypervisor and Kernel may allow information disclosure. System software adversary with a privileged user combined with a high complexity attack may enable data exposure. This result may potentially occur via local access when attack requirements are not present without special internal knowledge and requires no user interaction. The potential vulnerability may impact the confidentiality (none), integrity (none) and availability (none) of the vulnerable system, resulting in subsequent system confidentiality (high), integrity (none) and availability (none) impacts.
(CVE-2026-20917)

Tenable has extracted the preceding description block directly from the tested product security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

Solution

Run 'yum update microcode_ctl' or or 'yum update --advisory ALAS2-2026-3872' to update your system.

Plugin Details

Severity: High

ID: 341906

File Name: al2_ALAS-2026-3872.nasl

Version: 1.1

Type: Local

Agent: unix

Family: Amazon Linux Local Security Checks

Published: 8/31/2026

Updated: 8/31/2026

Supported Sensors: Agentless Assessment, Continuous Assessment, Frictionless Assessment Agent, Frictionless Assessment AWS, Nessus Agent, Tenable Cloud Security, Tenable Self-Hosted Container Security, Nessus

Risk Information

VPR

Risk Factor: Medium

Score: 4.9

Percentile: 58.15

CVSS v2

Risk Factor: Medium

Base Score: 6

Temporal Score: 4.4

Vector: CVSS2#AV:L/AC:H/Au:S/C:C/I:C/A:C

CVSS Score Source: CVE-2026-20716

CVSS v3

Risk Factor: High

Base Score: 7

Temporal Score: 6.1

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

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

CVSS v4

Risk Factor: High

Base Score: 7.2

Threat Score: 4.1

Threat Vector: CVSS:4.0/E:U

Vector: CVSS:4.0/AV:L/AC:H/AT:P/PR:L/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

Vulnerability Information

CPE: cpe:/o:amazon:linux:2, p-cpe:/a:amazon:linux:microcode_ctl-debuginfo, p-cpe:/a:amazon:linux:microcode_ctl

Required KB Items: Host/local_checks_enabled, Host/AmazonLinux/release, Host/AmazonLinux/rpm-list

Exploit Ease: No known exploits are available

Patch Publication Date: 8/31/2026

Vulnerability Publication Date: 8/11/2026

Reference Information

CVE: CVE-2025-31936, CVE-2025-31938, CVE-2025-35973, CVE-2026-20707, CVE-2026-20713, CVE-2026-20716, CVE-2026-20901, CVE-2026-20917

Detections

Analytics