SB2021010619 - Ubuntu update for linux

Description

This security bulletin contains information about 6 secuirty vulnerabilities.

1) Use-after-free (CVE-ID: CVE-2020-25656)

The vulnerability allows a local user to gain access to sensitive information.

The vulnerability exists due to a use-after-free error in the way the console subsystem uses KDGKBSENT and KDSKBSENT IOCTLs. A local user can run a specially crafted program to trigger an out-of-bounds read and gain access to sensitive information.

2) Use-after-free (CVE-ID: CVE-2020-25668)

The vulnerability allows a local authenticated user to escalate privileges on the system.

The vulnerability exists due to a use-after-free error within the con_font_op. A local authenticated user can trigger a use-after-free error and escalate privileges on the system.

3) Memory leak (CVE-ID: CVE-2020-25704)

The vulnerability allows a local user to perform a denial of service (DoS) attack.

The vulnerability exists due to memory leak within the Linux kernel performance monitoring subsystem when using PERF_EVENT_IOC_SET_FILTER. A local user could use this flaw to starve the resources causing denial of service.

4) NULL pointer dereference (CVE-ID: CVE-2020-27675)

The vulnerability allows a local user to perform a denial of service (DoS) attack.

The vulnerability exists due to a NULL pointer dereference error in drivers/xen/events/events_base.c. A malicious guest can trigger a dom0 crash by sending events for a paravirtualized device while simultaneously performing its reconfiguration.

5) Missing Authorization (CVE-ID: CVE-2020-27777)

The vulnerability allows a local user to escalate privileges on the system.

The vulnerability exists due to the way RTAS handles memory accesses in userspace to kernel communication. On a locked down (usually due to Secure Boot) guest system running on top of PowerVM or KVM hypervisors (pseries platform) a root like user could use this flaw to further increase their privileges to that of a running kernel.

6) Out-of-bounds read (CVE-ID: CVE-2020-28974)

The vulnerability allows a local privileged user to read and manipulate data.

The vulnerability exists due to an out-of-bounds read error within the con_font_default() and con_font_op() functions in drivers/tty/vt/vt.c. A local privileged user can read and manipulate data.

Remediation

Install update from vendor's website.

References

• https://ubuntu.com/security/notices/USN-4679-1