CVE-2021-3656

Description

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.

CVSS Metrics

• v3.1•HIGH•Score: 8.8CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
• v2.0•HIGH•Score: 7.2AV:L/AC:L/Au:N/C:C/I:C/A:C

EPSS Trends

Current EPSS score: 0.07%• Percentile: 21%

Techniques & Countermeasures

• CWE-862•Missing Authorization

  The product does not perform an authorization check when an actor attempts to access a resource or perform an action.

Affected Systems

• fedoraproject•fedora

  33 | 34

• linux•linux_kernel

  ≥ 4.13, < 4.14.245 | ≥ 4.15, < 4.19.205 | ≥ 4.20, < 5.4.142 | ≥ 5.5, < 5.10.60 | ≥ 5.11, < 5.13.12 | 5.14 | 5.14:rc1 | 5.14:rc2 | 5.14:rc3 | 5.14:rc4 | 5.14:rc5 | 5.14:rc6

• redhat•3scale_api_management

  2.0

• redhat•codeready_linux_builder

  na

• redhat•enterprise_linux

  8.0

• redhat•enterprise_linux_desktop

  7.0

• redhat•enterprise_linux_eus

  8.1 | 8.2 | 8.4

• redhat•enterprise_linux_for_ibm_z_systems

  7.0 | 8.0

• redhat•enterprise_linux_for_ibm_z_systems_eus

  8.1 | 8.2 | 8.4

• redhat•enterprise_linux_for_power_big_endian

  7.0

• redhat•enterprise_linux_for_power_little_endian

  7.0 | 8.0

• redhat•enterprise_linux_for_power_little_endian_eus

  8.1 | 8.2 | 8.4

• redhat•enterprise_linux_for_real_time

  7 | 8

• redhat•enterprise_linux_for_real_time_for_nfv

  7 | 8

• redhat•enterprise_linux_for_real_time_for_nfv_tus

  8.2 | 8.4

• redhat•enterprise_linux_for_real_time_tus

  8.2 | 8.4

• redhat•enterprise_linux_for_scientific_computing

  7.0

• redhat•enterprise_linux_server

  7.0

• redhat•enterprise_linux_server_aus

  7.6 | 7.7 | 8.2 | 8.4

• redhat•enterprise_linux_server_for_power_little_endian_update_services_for_sap_solutions

  7.6 | 8.1 | 8.2 | 8.4

• redhat•enterprise_linux_server_tus

  7.6 | 7.7 | 8.2 | 8.4

• redhat•enterprise_linux_server_update_services_for_sap_solutions

  7.6 | 7.7 | 8.1 | 8.2 | 8.4

• redhat•enterprise_linux_workstation

  7.0

• redhat•openstack

  13

• redhat•software_collections

  na

• redhat•virtualization_host

  4.0

References (4)

• https://www.openwall.com/lists/oss-security/2021/08/16/1
• https://git.kernel.org/pub/scm/virt/kvm/kvm.git/commit/?id=c7dfa4009965a9b2d7b329ee970eb8da0d32f0bc
• https://github.com/torvalds/linux/commit/c7dfa4009965a9b2d7b329ee970eb8da0d32f0bc
• https://bugzilla.redhat.com/show_bug.cgi?id=1983988