Ubuntu update for linux

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

Update the affected package linux to the latest version.

Vulnerable software versions

Ubuntu: 14.04 - 16.04

linux-image-virtual-lts-xenial (Ubuntu package): before 4.4.01097.106

linux-image-lowlatency-lts-xenial (Ubuntu package): before 4.4.01097.106

linux-image-generic-lts-xenial (Ubuntu package): before 4.4.01097.106

linux-image-4.4.0-1096-aws (Ubuntu package): before 4.4.01097.106

linux-image-virtual (Ubuntu package): before 4.4.01097.106

linux-image-lowlatency (Ubuntu package): before 4.4.01097.106

linux-image-kvm (Ubuntu package): before 4.4.01097.106

linux-image-generic (Ubuntu package): before 4.4.01097.106

linux-image-aws (Ubuntu package): before 4.4.01097.106

linux-image-4.4.0-214-lowlatency (Ubuntu package): before 4.4.01097.106

linux-image-4.4.0-214-generic (Ubuntu package): before 4.4.01097.106

linux-image-4.4.0-1132-aws (Ubuntu package): before 4.4.01097.106

linux-image-4.4.0-1097-kvm (Ubuntu package): before 4.4.01097.106

CPE2.3

• cpe:2.3:o:canonical:ubuntu:14.04:*:*:*:*:*:*:*
• cpe:2.3:o:canonical:ubuntu:16.04:*:*:*:*:*:*:*
• cpe:2.3:a:canonical:linux-image-virtual-lts-xenial_ubuntu_package:*:*:*:*:*:ubuntu:*:*
• cpe:2.3:a:canonical:linux-image-lowlatency-lts-xenial_ubuntu_package:*:*:*:*:*:ubuntu:*:*
• cpe:2.3:a:canonical:linux-image-generic-lts-xenial_ubuntu_package:*:*:*:*:*:ubuntu:*:*
• cpe:2.3:a:canonical:linux-image-4.4.0-1096-aws_ubuntu_package:*:*:*:*:*:ubuntu:*:*
• cpe:2.3:a:canonical:linux-image-virtual_ubuntu_package:*:*:*:*:*:ubuntu:*:*
• cpe:2.3:a:canonical:linux-image-lowlatency_ubuntu_package:*:*:*:*:*:ubuntu:*:*
• cpe:2.3:a:canonical:linux-image-kvm_ubuntu_package:*:*:*:*:*:ubuntu:*:*
• cpe:2.3:a:canonical:linux-image-generic_ubuntu_package:*:*:*:*:*:ubuntu:*:*
• cpe:2.3:a:canonical:linux-image-aws_ubuntu_package:*:*:*:*:*:ubuntu:*:*
• cpe:2.3:a:canonical:linux-image-4.4.0-214-lowlatency_ubuntu_package:*:*:*:*:*:ubuntu:*:*
• cpe:2.3:a:canonical:linux-image-4.4.0-214-generic_ubuntu_package:*:*:*:*:*:ubuntu:*:*
• cpe:2.3:a:canonical:linux-image-4.4.0-1132-aws_ubuntu_package:*:*:*:*:*:ubuntu:*:*
• cpe:2.3:a:canonical:linux-image-4.4.0-1097-kvm_ubuntu_package:*:*:*:*:*:ubuntu:*:*

External links

https://ubuntu.com/security/notices/USN-5062-1

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.