Ubuntu update for linux

Published: 2021-09-08

Risk	Low
Patch available	YES
Number of vulnerabilities	10
CVE-ID	CVE-2021-3656 CVE-2021-3653 CVE-2020-26541 CVE-2021-22543 CVE-2021-34693 CVE-2021-3612 CVE-2021-38198 CVE-2021-38200 CVE-2021-38206 CVE-2021-38207
CWE-ID	CWE-264 CWE-693 CWE-119 CWE-908 CWE-787 CWE-732 CWE-476 CWE-120
Exploitation vector	Network
Public exploit	Public exploit code for vulnerability #4 is available.
Vulnerable software	Ubuntu Operating systems & Components / Operating system linux-image-raspi (Ubuntu package) Operating systems & Components / Operating system package or component linux-image-virtual-hwe-20.04 (Ubuntu package) Operating systems & Components / Operating system package or component linux-image-generic-64k-hwe-20.04 (Ubuntu package) Operating systems & Components / Operating system package or component linux-image-generic-lpae-hwe-20.04 (Ubuntu package) Operating systems & Components / Operating system package or component linux-image-generic-hwe-20.04 (Ubuntu package) Operating systems & Components / Operating system package or component linux-image-lowlatency-hwe-20.04 (Ubuntu package) Operating systems & Components / Operating system package or component linux-image-lowlatency (Ubuntu package) Operating systems & Components / Operating system package or component linux-image-generic-64k (Ubuntu package) Operating systems & Components / Operating system package or component linux-image-generic-lpae (Ubuntu package) Operating systems & Components / Operating system package or component linux-image-kvm (Ubuntu package) Operating systems & Components / Operating system package or component linux-image-5.11.0-1015-azure (Ubuntu package) Operating systems & Components / Operating system package or component linux-image-5.11.0-34-generic-64k (Ubuntu package) Operating systems & Components / Operating system package or component linux-image-oracle (Ubuntu package) Operating systems & Components / Operating system package or component linux-image-5.11.0-1018-gcp (Ubuntu package) Operating systems & Components / Operating system package or component linux-image-gcp (Ubuntu package) Operating systems & Components / Operating system package or component linux-image-gke (Ubuntu package) Operating systems & Components / Operating system package or component linux-image-oem-20.04 (Ubuntu package) Operating systems & Components / Operating system package or component linux-image-raspi-nolpae (Ubuntu package) Operating systems & Components / Operating system package or component linux-image-azure (Ubuntu package) Operating systems & Components / Operating system package or component linux-image-5.11.0-1017-raspi-nolpae (Ubuntu package) Operating systems & Components / Operating system package or component linux-image-5.11.0-34-generic-lpae (Ubuntu package) Operating systems & Components / Operating system package or component linux-image-5.11.0-1017-oracle (Ubuntu package) Operating systems & Components / Operating system package or component linux-image-5.11.0-1017-raspi (Ubuntu package) Operating systems & Components / Operating system package or component linux-image-5.11.0-1015-kvm (Ubuntu package) Operating systems & Components / Operating system package or component linux-image-aws (Ubuntu package) Operating systems & Components / Operating system package or component linux-image-generic (Ubuntu package) Operating systems & Components / Operating system package or component linux-image-5.11.0-1017-aws (Ubuntu package) Operating systems & Components / Operating system package or component linux-image-virtual (Ubuntu package) Operating systems & Components / Operating system package or component linux-image-5.11.0-34-lowlatency (Ubuntu package) Operating systems & Components / Operating system package or component linux-image-5.11.0-34-generic (Ubuntu package) Operating systems & Components / Operating system package or component
Vendor	Canonical Ltd.

Security Bulletin

This security bulletin contains information about 10 vulnerabilities.

1) Security restrictions bypass

EUVDB-ID: #VU56929

Risk: Low

CVSSv4.0: 5.9 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Clear]

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.

Mitigation

Update the affected package linux to the latest version.

Vulnerable software versions

Ubuntu: 20.04 - 21.04

linux-image-raspi (Ubuntu package): before 5.11.0.1017.15

linux-image-virtual-hwe-20.04 (Ubuntu package): before 5.11.0.34.36~20.04.13

linux-image-generic-64k-hwe-20.04 (Ubuntu package): before 5.11.0.34.36~20.04.13

linux-image-generic-lpae-hwe-20.04 (Ubuntu package): before 5.11.0.34.36~20.04.13

linux-image-generic-hwe-20.04 (Ubuntu package): before 5.11.0.34.36~20.04.13

linux-image-lowlatency-hwe-20.04 (Ubuntu package): before 5.11.0.34.36~20.04.13

linux-image-lowlatency (Ubuntu package): before 5.11.0.34.36

linux-image-generic-64k (Ubuntu package): before 5.11.0.34.36

linux-image-generic-lpae (Ubuntu package): before 5.11.0.34.36

linux-image-kvm (Ubuntu package): before 5.11.0.1015.16

linux-image-5.11.0-1015-azure (Ubuntu package): before 5.11.0-1015.16~20.04.1

linux-image-5.11.0-34-generic-64k (Ubuntu package): before 5.11.0-34.36~20.04.1

linux-image-oracle (Ubuntu package): before 5.11.0.1017.18~20.04.10

linux-image-5.11.0-1018-gcp (Ubuntu package): before 5.11.0-1018.20

linux-image-gcp (Ubuntu package): before 5.11.0.1018.18

linux-image-gke (Ubuntu package): before 5.11.0.1018.18

linux-image-oem-20.04 (Ubuntu package): before 5.11.0.34.36

linux-image-raspi-nolpae (Ubuntu package): before 5.11.0.1017.15

linux-image-azure (Ubuntu package): before 5.11.0.1015.16

linux-image-5.11.0-1017-raspi-nolpae (Ubuntu package): before 5.11.0-1017.18

linux-image-5.11.0-34-generic-lpae (Ubuntu package): before 5.11.0-34.36~20.04.1

linux-image-5.11.0-1017-oracle (Ubuntu package): before 5.11.0-1017.18~20.04.1

linux-image-5.11.0-1017-raspi (Ubuntu package): before 5.11.0-1017.18

linux-image-5.11.0-1015-kvm (Ubuntu package): before 5.11.0-1015.16

linux-image-aws (Ubuntu package): before 5.11.0.1017.18~20.04.16

linux-image-generic (Ubuntu package): before 5.11.0.34.36

linux-image-5.11.0-1017-aws (Ubuntu package): before 5.11.0-1017.18~20.04.1

linux-image-virtual (Ubuntu package): before 5.11.0.34.36

linux-image-5.11.0-34-lowlatency (Ubuntu package): before 5.11.0-34.36~20.04.1

linux-image-5.11.0-34-generic (Ubuntu package): before 5.11.0-34.36~20.04.1

CPE2.3

External links

https://ubuntu.com/security/notices/USN-5070-1

Q & A

Can this vulnerability be exploited remotely?

No. This vulnerability can be exploited locally. The attacker should have authentication credentials and successfully authenticate on the system.

Is there known malware, which exploits this vulnerability?

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

2) 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.