Red Hat Enterprise Linux 8.1 update for kernel

Published: 2021-09-29

Risk	Low
Patch available	YES
Number of vulnerabilities	2
CVE-ID	CVE-2021-3653 CVE-2021-3656
CWE-ID	CWE-264
Exploitation vector	Network
Public exploit	N/A
Vulnerable software Subscribe	kernel (Red Hat package) Operating systems & Components / Operating system package or component Red Hat Enterprise Linux Server for x86_64 - Update Services for SAP Solutions Operating systems & Components / Operating system package or component Red Hat Enterprise Linux Server for Power LE - Update Services for SAP Solutions Operating systems & Components / Operating system package or component Red Hat CodeReady Linux Builder for ARM 64 - Extended Update Support Operating systems & Components / Operating system Red Hat CodeReady Linux Builder for Power, little endian - Extended Update Support Operating systems & Components / Operating system Red Hat CodeReady Linux Builder for x86_64 - Extended Update Support Operating systems & Components / Operating system Red Hat Enterprise Linux for ARM 64 - Extended Update Support Operating systems & Components / Operating system Red Hat Enterprise Linux for Power, little endian - Extended Update Support Operating systems & Components / Operating system Red Hat Enterprise Linux for IBM z Systems - Extended Update Support Operating systems & Components / Operating system Red Hat Enterprise Linux for x86_64 - Extended Update Support Operating systems & Components / Operating system
Vendor	Red Hat Inc.

Security Bulletin

This security bulletin contains information about 2 vulnerabilities.

1) Security restrictions bypass

EUVDB-ID: #VU56904

Risk: Low

CVSSv3.1: 6.5 [CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C]

CVE-ID: CVE-2021-3653

CWE-ID: CWE-264 - Permissions, Privileges, and Access Controls

Exploit availability: No

Description

The vulnerability allows a malicious guest to escalate privileges on the system.

The vulnerability exists due to improperly imposed security restrictions within 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.

Mitigation

Install updates from vendor's website.

Vulnerable software versions

kernel (Red Hat package): 4.18.0-147.0.2.el8_1 - 4.18.0-147.52.1.el8_1

Red Hat CodeReady Linux Builder for ARM 64 - Extended Update Support: 8.1

Red Hat CodeReady Linux Builder for Power, little endian - Extended Update Support: 8.1

Red Hat CodeReady Linux Builder for x86_64 - Extended Update Support: 8.1

Red Hat Enterprise Linux for ARM 64 - Extended Update Support: 8.1

Red Hat Enterprise Linux for Power, little endian - Extended Update Support: 8.1

Red Hat Enterprise Linux for IBM z Systems - Extended Update Support: 8.1

Red Hat Enterprise Linux for x86_64 - Extended Update Support: 8.1

Red Hat Enterprise Linux Server for x86_64 - Update Services for SAP Solutions: 8.1

Red Hat Enterprise Linux Server for Power LE - Update Services for SAP Solutions: 8.1

CPE2.3

External links

http://access.redhat.com/errata/RHSA-2021:3676

Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote authenticated user via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.

2) Security restrictions bypass

EUVDB-ID: #VU56929

Risk: Low

CVSSv3.1: 6.8 [CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C]

CVE-ID: CVE-2021-3656

CWE-ID: CWE-264 - Permissions, Privileges, and Access Controls

Exploit availability: No

Description

The vulnerability allows a malicious guest to escalate privileges on the system.

The vulnerability exists due to improperly imposed security restrictions within 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.

The vulnerability allows the L2 guest 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.