SB2021090851 - Ubuntu update for linux
Published: September 8, 2021
Breakdown by Severity
- Low
- Medium
- High
- Critical
Description
This security bulletin contains information about 10 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) Protection Mechanism Failure (CVE-ID: CVE-2020-26541)
The vulnerability allows a local user to escalate privileges on the system.
The Linux kernel through 5.8.13 does not properly enforce the Secure
Boot Forbidden Signature Database (aka dbx) protection mechanism. This
affects certs/blacklist.c and certs/system_keyring.c. A local user can escalate privileges on the system.
4) Buffer overflow (CVE-ID: CVE-2021-22543)
The vulnerability allows a local user to escalate privileges on the system.
The vulnerability exists due to a boundary error in Linux kernel when handling VM_IO|VM_PFNMAP vmas in KVM. A local user can can bypass RO checks and cause the pages to get freed while still accessible by the VMM and guest. As a result, an attacker with the ability to start and control a VM to read/write random pages of memory, can trigger memory corruption and execute arbitrary code with elevated privileges.
5) 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.
6) 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.
7) Incorrect permission assignment for critical resource (CVE-ID: CVE-2021-38198)
The vulnerability allows a local user to perform a denial of service attack.The vulnerability exists due to arch/x86/kvm/mmu/paging_tmpl.h incorrectly computes the access permissions of a shadow page. A local user can trigger an error to perform a denial of service attack.
8) Null pointer dereference (CVE-ID: CVE-2021-38200)
The vulnerability allows a local user to perform a denial of service (DoS) attack.
arch/powerpc/perf/core-book3s.c in the Linux kernel before 5.12.13, on systems with perf_event_paranoid=-1 and no specific PMU driver support registered, allows local users to cause a denial of service (perf_instruction_pointer NULL pointer dereference and OOPS) via a 'perf record' command.
9) Null pointer dereference (CVE-ID: CVE-2021-38206)
The vulnerability allows a local user to perform a denial of service (DoS) attack.
The mac80211 subsystem in the Linux kernel before 5.12.13, when a device supporting only 5 GHz is used, allows attackers to cause a denial of service (NULL pointer dereference in the radiotap parser) by injecting a frame with 802.11a rates.
10) Buffer overflow (CVE-ID: CVE-2021-38207)
The vulnerability allows a remote non-authenticated attacker to perform a denial of service (DoS) attack.
drivers/net/ethernet/xilinx/ll_temac_main.c in the Linux kernel before 5.12.13 allows remote attackers to cause a denial of service (buffer overflow and lockup) by sending heavy network traffic for about 10 minutes.
Remediation
Install update from vendor's website.