SB2021091718 - Ubuntu update for linux-gcp
Published: September 17, 2021
Breakdown by Severity
- Low
- Medium
- High
- Critical
Description
This security bulletin contains information about 4 secuirty vulnerabilities.
1) Security restrictions bypass (CVE-ID: CVE-2021-3656)
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.
2) Security restrictions bypass (CVE-ID: CVE-2021-3653)
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.
3) Use of uninitialized resource (CVE-ID: CVE-2021-34693)
The vulnerability allows a local user to gain access to sensitive information.
The vulnerability exists due to net/can/bcm.c in the Linux kernel through 5.12.10 allows local users to obtain sensitive information from kernel stack memory because parts of a data structure are uninitialized.
4) Out-of-bounds write (CVE-ID: CVE-2021-3612)
The vulnerability allows a local user to escalate privileges on the system.
The vulnerability exists due to a boundary error in joystick devices subsystem in Linux kernel. A local user can make a specially crafted JSIOCSBTNMAP IOCTL call, trigger out-of-bounds write and execute arbitrary code with escalated privileges.
Remediation
Install update from vendor's website.