Red Hat Enterprise Linux 8 update for kernel

1) Security restrictions bypass

EUVDB-ID: #VU56904

Risk: Low

CVSSv4.0: 5.2 [CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Clear]

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

Red Hat CodeReady Linux Builder for Power, little endian - Extended Update Support: 8.4

Red Hat CodeReady Linux Builder for ARM 64 - Extended Update Support: 8.4

Red Hat CodeReady Linux Builder for x86_64 - Extended Update Support: 8.4

Red Hat Enterprise Linux Server - TUS: 8.4

Red Hat Enterprise Linux for Power, little endian - Extended Update Support: 8.4

Red Hat Enterprise Linux for IBM z Systems - Extended Update Support: 8.4

Red Hat Enterprise Linux Server - AUS: 8.4

Red Hat Enterprise Linux for x86_64 - Extended Update Support: 8.4

Red Hat Enterprise Linux for ARM 64 - Extended Update Support: 8.4

Red Hat CodeReady Linux Builder for ARM 64: 8.0

Red Hat CodeReady Linux Builder for Power, little endian: 8.0

Red Hat CodeReady Linux Builder for x86_64: 8.0

Red Hat Enterprise Linux for ARM 64: 8

Red Hat Enterprise Linux for Power, little endian: 8

Red Hat Enterprise Linux for IBM z Systems: 8

Red Hat Enterprise Linux for x86_64: 8.0

kernel (Red Hat package): before 4.18.0-305.19.1.el8_4

CPE2.3

• cpe:2.3:o:red_hat:red_hat_codeready_linux_builder_for_power_little_endian_-_extended_update_support:8.4:*:*:*:*:red_hat_enterprise_linux:*:*
• cpe:2.3:o:red_hat:red_hat_codeready_linux_builder_for_arm_64_-_extended_update_support:8.4:*:*:*:*:red_hat_enterprise_linux:*:*
• cpe:2.3:o:red_hat:red_hat_codeready_linux_builder_for_x86_64_-_extended_update_support:8.4:*:*:*:*:red_hat_enterprise_linux:*:*
• cpe:2.3:o:red_hat:red_hat_enterprise_linux_server_-_tus:8.4:*:*:*:*:red_hat_enterprise_linux:*:*
• cpe:2.3:o:red_hat:red_hat_enterprise_linux_for_power_little_endian_-_extended_update_support:8.4:*:*:*:*:red_hat_enterprise_linux:*:*
• cpe:2.3:o:red_hat:red_hat_enterprise_linux_for_ibm_z_systems_-_extended_update_support:8.4:*:*:*:*:red_hat_enterprise_linux:*:*
• cpe:2.3:o:red_hat:red_hat_enterprise_linux_server_-_aus:8.4:*:*:*:*:red_hat_enterprise_linux:*:*
• cpe:2.3:o:red_hat:red_hat_enterprise_linux_for_x86_64_-_extended_update_support:8.4:*:*:*:*:red_hat_enterprise_linux:*:*
• cpe:2.3:o:red_hat:red_hat_enterprise_linux_for_arm_64_-_extended_update_support:8.4:*:*:*:*:red_hat_enterprise_linux:*:*
• cpe:2.3:o:red_hat:red_hat_codeready_linux_builder_for_arm_64:8.0:*:*:*:*:red_hat_enterprise_linux:*:*
• cpe:2.3:o:red_hat:red_hat_codeready_linux_builder_for_power_little_endian:8.0:*:*:*:*:red_hat_enterprise_linux:*:*
• cpe:2.3:o:red_hat:red_hat_codeready_linux_builder_for_x86_64:8.0:*:*:*:*:red_hat_enterprise_linux:*:*
• cpe:2.3:o:red_hat:red_hat_enterprise_linux_for_arm_64:8:*:*:*:*:red_hat_enterprise_linux:*:*
• cpe:2.3:o:red_hat:red_hat_enterprise_linux_for_power_little_endian:8:*:*:*:*:red_hat_enterprise_linux:*:*
• cpe:2.3:o:red_hat:red_hat_enterprise_linux_for_ibm_z_systems:8:*:*:*:*:red_hat_enterprise_linux:*:*
• cpe:2.3:o:red_hat:red_hat_enterprise_linux:8.0:*:*:*:*:*:*:*
• cpe:2.3:a:red_hat:kernel_redhat_package:*:*:*:*:*:red_hat_enterprise_linux:*:*

External links

https://access.redhat.com/errata/RHSA-2021:3548

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.