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Ubuntu 18.04 LTS / 20.04 LTS : Linux kernel vulnerabilities (USN-4679-1)

high Nessus Plugin ID 144750

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Synopsis

The remote Ubuntu host is missing one or more security updates.

Description

The remote Ubuntu 18.04 LTS / 20.04 LTS host has a package installed that is affected by multiple vulnerabilities as referenced in the USN-4679-1 advisory.

 - A flaw was found in the Linux kernel. A use-after-free was found in the way the console subsystem was using ioctls KDGKBSENT and KDSKBSENT. A local user could use this flaw to get read memory access out of bounds. The highest threat from this vulnerability is to data confidentiality. (CVE-2020-25656)

 - A flaw was found in Linux Kernel because access to the global variable fg_console is not properly synchronized leading to a use after free in con_font_op. (CVE-2020-25668)

 - A flaw memory leak in the Linux kernel performance monitoring subsystem was found in the way if using PERF_EVENT_IOC_SET_FILTER. A local user could use this flaw to starve the resources causing denial of service. (CVE-2020-25704)

 - An issue was discovered in the Linux kernel through 5.9.1, as used with Xen through 4.14.x.
 drivers/xen/events/events_base.c allows event-channel removal during the event-handling loop (a race condition). This can cause a use-after-free or NULL pointer dereference, as demonstrated by a dom0 crash via events for an in-reconfiguration paravirtualized device, aka CID-073d0552ead5. (CVE-2020-27675)

 - A flaw was found in the way RTAS handled 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 local user could use this flaw to further increase their privileges to that of a running kernel. (CVE-2020-27777)

 - A slab-out-of-bounds read in fbcon in the Linux kernel before 5.9.7 could be used by local attackers to read privileged information or potentially crash the kernel, aka CID-3c4e0dff2095. This occurs because KD_FONT_OP_COPY in drivers/tty/vt/vt.c can be used for manipulations such as font height. (CVE-2020-28974)

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

Solution

Update the affected kernel package.

See Also

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

Plugin Details

Severity: High

ID: 144750

File Name: ubuntu_USN-4679-1.nasl

Version: 1.8

Type: local

Agent: unix

Published: 1/6/2021

Updated: 1/9/2024

Supported Sensors: Frictionless Assessment AWS, Frictionless Assessment Azure, Frictionless Assessment Agent, Nessus Agent, Agentless Assessment, Nessus

Risk Information

VPR

Risk Factor: Medium

Score: 6.7

CVSS v2

Risk Factor: High

Base Score: 7.2

Temporal Score: 5.6

Vector: CVSS2#AV:L/AC:L/Au:N/C:C/I:C/A:C

CVSS Score Source: CVE-2020-27777

CVSS v3

Risk Factor: High

Base Score: 7

Temporal Score: 6.3

Vector: CVSS:3.0/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

Temporal Vector: CVSS:3.0/E:P/RL:O/RC:C

CVSS Score Source: CVE-2020-25668

Vulnerability Information

CPE: cpe:/o:canonical:ubuntu_linux:18.04:-:lts, cpe:/o:canonical:ubuntu_linux:20.04:-:lts, p-cpe:/a:canonical:ubuntu_linux:linux-image-5.4.0-1026-raspi, p-cpe:/a:canonical:ubuntu_linux:linux-image-5.4.0-1031-kvm, p-cpe:/a:canonical:ubuntu_linux:linux-image-5.4.0-1033-gcp, p-cpe:/a:canonical:ubuntu_linux:linux-image-5.4.0-1033-gke, p-cpe:/a:canonical:ubuntu_linux:linux-image-5.4.0-1034-oracle, p-cpe:/a:canonical:ubuntu_linux:linux-image-5.4.0-1035-azure, p-cpe:/a:canonical:ubuntu_linux:linux-image-5.4.0-59-generic, p-cpe:/a:canonical:ubuntu_linux:linux-image-5.4.0-59-generic-lpae, p-cpe:/a:canonical:ubuntu_linux:linux-image-5.4.0-59-lowlatency

Required KB Items: Host/cpu, Host/Debian/dpkg-l, Host/Ubuntu, Host/Ubuntu/release

Exploit Available: true

Exploit Ease: Exploits are available

Patch Publication Date: 1/6/2021

Vulnerability Publication Date: 10/22/2020

Reference Information

CVE: CVE-2020-25656, CVE-2020-25668, CVE-2020-25704, CVE-2020-27675, CVE-2020-27777, CVE-2020-28974

USN: 4679-1