Detections
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Amazon Linux 2 : kernel (ALAS-2021-1704)

high Nessus Plugin ID 153418

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Synopsis

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

Description

The version of kernel installed on the remote host is prior to 4.14.246-187.474. It is, therefore, affected by multiple vulnerabilities as referenced in the ALAS2-2021-1704 advisory.

 - A flaw was found in the KVM's AMD code for supporting SVM nested virtualization. The flaw occurs when processing the VMCB (virtual machine control block) provided by the L1 guest to spawn/handle a nested guest (L2). Due to improper validation of the virt_ext field, this issue could allow a malicious L1 to disable both VMLOAD/VMSAVE intercepts and VLS (Virtual VMLOAD/VMSAVE) for the L2 guest. As a result, the L2 guest would be allowed to read/write physical pages of the host, resulting in a crash of the entire system, leak of sensitive data or potential guest-to-host escape. (CVE-2021-3656)

 - A flaw was found in the KVM's AMD code for supporting SVM nested virtualization. The flaw occurs when processing the VMCB (virtual machine control block) provided by the L1 guest to spawn/handle a nested guest (L2). Due to improper validation of the int_ctl field, this issue could allow a malicious L1 to enable AVIC support (Advanced Virtual Interrupt Controller) for the L2 guest. As a result, the L2 guest would be allowed to read/write physical pages of the host, resulting in a crash of the entire system, leak of sensitive data or potential guest-to-host escape. This flaw affects Linux kernel versions prior to 5.14-rc7. (CVE-2021-3653)

 - A security issue was found in Linux kernel's OverlayFS subsystem where a local attacker who has the ability to mount the TmpFS filesystem with OverlayFS can abuse a logic bug in the overlayfs code which can inadvertently reveal files hidden in the original mount. (CVE-2021-3732)

 - A race problem was seen in the vt_k_ioctl in drivers/tty/vt/vt_ioctl.c in the Linux kernel, which may cause an out of bounds read in vt as the write access to vc_mode is not protected by lock-in vt_ioctl (KDSETMDE). The highest threat from this vulnerability is to data confidentiality. (CVE-2021-3753)

 - arch/x86/kvm/mmu/paging_tmpl.h in the Linux kernel before 5.12.11 incorrectly computes the access permissions of a shadow page, leading to a missing guest protection page fault. (CVE-2021-38198)

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

Solution

Run 'yum update kernel' to update your system.

See Also

https://alas.aws.amazon.com/AL2/ALAS-2021-1704.html

https://access.redhat.com/security/cve/CVE-2021-3653

https://access.redhat.com/security/cve/CVE-2021-3656

https://access.redhat.com/security/cve/CVE-2021-3732

https://access.redhat.com/security/cve/CVE-2021-3753

https://access.redhat.com/security/cve/CVE-2021-38198

https://access.redhat.com/security/cve/CVE-2021-40490

Plugin Details

Severity: High

ID: 153418

File Name: al2_ALAS-2021-1704.nasl

Version: 1.10

Type: local

Agent: unix

Published: 9/16/2021

Updated: 11/30/2023

Supported Sensors: Frictionless Assessment AWS, Frictionless Assessment Agent, Nessus Agent, Agentless Assessment, Nessus

Risk Information

VPR

Risk Factor: High

Score: 7.3

CVSS v2

Risk Factor: High

Base Score: 7.2

Temporal Score: 5.6

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

CVSS Score Source: CVE-2021-3656

CVSS v3

Risk Factor: High

Base Score: 8.8

Temporal Score: 7.9

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

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

Vulnerability Information

CPE: p-cpe:/a:amazon:linux:kernel, p-cpe:/a:amazon:linux:kernel-debuginfo, p-cpe:/a:amazon:linux:kernel-debuginfo-common-aarch64, p-cpe:/a:amazon:linux:kernel-debuginfo-common-x86_64, p-cpe:/a:amazon:linux:kernel-devel, p-cpe:/a:amazon:linux:kernel-headers, p-cpe:/a:amazon:linux:kernel-livepatch-4.14.246-187.474, p-cpe:/a:amazon:linux:kernel-tools, p-cpe:/a:amazon:linux:kernel-tools-debuginfo, p-cpe:/a:amazon:linux:kernel-tools-devel, p-cpe:/a:amazon:linux:perf, p-cpe:/a:amazon:linux:perf-debuginfo, p-cpe:/a:amazon:linux:python-perf, p-cpe:/a:amazon:linux:python-perf-debuginfo, cpe:/o:amazon:linux:2

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

Exploit Available: true

Exploit Ease: Exploits are available

Patch Publication Date: 9/8/2021

Vulnerability Publication Date: 8/8/2021

Reference Information

CVE: CVE-2021-3653, CVE-2021-3656, CVE-2021-3732, CVE-2021-3753, CVE-2021-38198, CVE-2021-40490

ALAS: 2021-1704