Ubuntu 16.04 LTS / 18.04 LTS / 20.04 LTS : Brotli vulnerability (USN-4568-1) - Nessus

Medium Plugin ID: 141179

This page contains detailed information about the Ubuntu 16.04 LTS / 18.04 LTS / 20.04 LTS : Brotli vulnerability (USN-4568-1) Nessus plugin including available exploits and PoCs found on GitHub, in Metasploit or Exploit-DB for verifying of this vulnerability.

Table Of Contents

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Plugin Overview
Vulnerability Information

Synopsis
Description
Solution

Public Exploits
Risk Information
Plugin Source
How to Run
References
Version

Plugin Overview

ID: 141179
Name: Ubuntu 16.04 LTS / 18.04 LTS / 20.04 LTS : Brotli vulnerability (USN-4568-1)
Filename: ubuntu_USN-4568-1.nasl
Vulnerability Published: 2020-09-15
This Plugin Published: 2020-10-05
Last Modification Time: 2020-11-24
Plugin Version: 1.2
Plugin Type: local
Plugin Family: Ubuntu Local Security Checks
Dependencies: ssh_get_info.nasl
Required KB Items [?]: Host/cpu, Host/Debian/dpkg-l, Host/Ubuntu, Host/Ubuntu/release

Vulnerability Information

Severity: Medium
Vulnerability Published: 2020-09-15
Patch Published: 2020-10-05
CVE [?]: CVE-2020-8927
CPE [?]: cpe:/o:canonical:ubuntu_linux:16.04:-:lts, cpe:/o:canonical:ubuntu_linux:18.04:-:lts, cpe:/o:canonical:ubuntu_linux:20.04:-:lts, p-cpe:/a:canonical:ubuntu_linux:brotli, p-cpe:/a:canonical:ubuntu_linux:libbrotli1, p-cpe:/a:canonical:ubuntu_linux:libbrotli-dev, p-cpe:/a:canonical:ubuntu_linux:python3-brotli, p-cpe:/a:canonical:ubuntu_linux:python-brotli

Synopsis

The remote Ubuntu host is missing a security update.

Description

The remote Ubuntu 16.04 LTS / 18.04 LTS / 20.04 LTS host has packages installed that are affected by a vulnerability as referenced in the USN-4568-1 advisory.

- A buffer overflow exists in the Brotli library versions prior to 1.0.8 where an attacker controlling the input length of a one-shot decompression request to a script can trigger a crash, which happens when copying over chunks of data larger than 2 GiB. It is recommended to update your Brotli library to 1.0.8 or later. If one cannot update, we recommend to use the streaming API as opposed to the one-shot API, and impose chunk size limits. (CVE-2020-8927)

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

Solution

Update the affected packages.

Public Exploits

Target Network Port(s): N/A
Target Asset(s): N/A
Exploit Available: True (GitHub)
Exploit Ease: Exploits (PoCs) are available

Here's the list of publicly known exploits and PoCs for verifying the Ubuntu 16.04 LTS / 18.04 LTS / 20.04 LTS : Brotli vulnerability (USN-4568-1) vulnerability:

GitHub: https://github.com/jaydenaung/CloudGuard-ShiftLeft-CICD-AWS
[CVE-2020-8927]

Before running any exploit against any system, make sure you are authorized by the owner of the target system(s) to perform such activity. In any other case, this would be considered as an illegal activity.

WARNING: Beware of using unverified exploits from sources such as GitHub or Exploit-DB. These exploits and PoCs could contain malware. For more information, see how to use exploits safely.

Risk Information

CVSS Score Source [?]: CVE-2020-8927
CVSS V2 Vector: AV:N/AC:L/Au:N/C:N/I:P/A:P/E:U/RL:OF/RC:C

CVSS Base Score:	6.4 (Medium)
Impact Subscore:	4.9
Exploitability Subscore:	10.0
CVSS Temporal Score:	4.7 (Medium)
CVSS Environmental Score:	NA (None)
Modified Impact Subscore:	NA
Overall CVSS Score:	4.7 (Medium)

CVSS V3 Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L/E:U/RL:O/RC:C

CVSS Base Score:	6.5 (Medium)
Impact Subscore:	2.5
Exploitability Subscore:	3.9
CVSS Temporal Score:	5.7 (Medium)
CVSS Environmental Score:	NA (None)
Modified Impact Subscore:	NA
Overall CVSS Score:	5.7 (Medium)

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Plugin Source

#
# (C) Tenable Network Security, Inc.
#
# The descriptive text and package checks in this plugin were
# extracted from Ubuntu Security Notice USN-4568-1. The text
# itself is copyright (C) Canonical, Inc. See
# <http://www.ubuntu.com/usn/>. Ubuntu(R) is a registered
# trademark of Canonical, Inc.
#

include('compat.inc');

if (description)
{
  script_id(141179);
  script_version("1.2");
  script_set_attribute(attribute:"plugin_modification_date", value:"2020/11/24");

  script_cve_id("CVE-2020-8927");
  script_xref(name:"USN", value:"4568-1");

  script_name(english:"Ubuntu 16.04 LTS / 18.04 LTS / 20.04 LTS : Brotli vulnerability (USN-4568-1)");
  script_summary(english:"Checks the dpkg output for the updated packages");

  script_set_attribute(attribute:"synopsis", value:
"The remote Ubuntu host is missing a security update.");
  script_set_attribute(attribute:"description", value:
"The remote Ubuntu 16.04 LTS / 18.04 LTS / 20.04 LTS host has packages installed that are affected by a vulnerability as
referenced in the USN-4568-1 advisory.

  - A buffer overflow exists in the Brotli library versions prior to 1.0.8 where an attacker controlling the
    input length of a one-shot decompression request to a script can trigger a crash, which happens when
    copying over chunks of data larger than 2 GiB. It is recommended to update your Brotli library to 1.0.8 or
    later. If one cannot update, we recommend to use the streaming API as opposed to the one-shot API, and
    impose chunk size limits. (CVE-2020-8927)

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version
number.");
  script_set_attribute(attribute:"see_also", value:"https://ubuntu.com/security/notices/USN-4568-1");
  script_set_attribute(attribute:"solution", value:
"Update the affected packages.");
  script_set_cvss_base_vector("CVSS2#AV:N/AC:L/Au:N/C:N/I:P/A:P");
  script_set_cvss_temporal_vector("CVSS2#E:U/RL:OF/RC:C");
  script_set_cvss3_base_vector("CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L");
  script_set_cvss3_temporal_vector("CVSS:3.0/E:U/RL:O/RC:C");
  script_set_attribute(attribute:"cvss_score_source", value:"CVE-2020-8927");

  script_set_attribute(attribute:"exploitability_ease", value:"No known exploits are available");

  script_set_attribute(attribute:"vuln_publication_date", value:"2020/09/15");
  script_set_attribute(attribute:"patch_publication_date", value:"2020/10/05");
  script_set_attribute(attribute:"plugin_publication_date", value:"2020/10/05");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:canonical:ubuntu_linux:16.04:-:lts");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:canonical:ubuntu_linux:18.04:-:lts");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:canonical:ubuntu_linux:20.04:-:lts");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:brotli");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:libbrotli-dev");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:libbrotli1");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:python-brotli");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:python3-brotli");
  script_end_attributes();

  script_category(ACT_GATHER_INFO);
  script_family(english:"Ubuntu Local Security Checks");

  script_copyright(english:"Ubuntu Security Notice (C) 2020 Canonical, Inc. / NASL script (C) 2020 and is owned by Tenable, Inc. or an Affiliate thereof.");

  script_dependencies("ssh_get_info.nasl");
  script_require_keys("Host/cpu", "Host/Ubuntu", "Host/Ubuntu/release", "Host/Debian/dpkg-l");

  exit(0);
}

include('audit.inc');
include('ubuntu.inc');
include('misc_func.inc');

if ( ! get_kb_item('Host/local_checks_enabled') ) audit(AUDIT_LOCAL_CHECKS_NOT_ENABLED);
release = get_kb_item('Host/Ubuntu/release');
if ( isnull(release) ) audit(AUDIT_OS_NOT, 'Ubuntu');
release = chomp(release);
if (! preg(pattern:"^(16\.04|18\.04|20\.04)$", string:release)) audit(AUDIT_OS_NOT, 'Ubuntu 16.04 / 18.04 / 20.04', 'Ubuntu ' + release);
if ( ! get_kb_item('Host/Debian/dpkg-l') ) audit(AUDIT_PACKAGE_LIST_MISSING);

cpu = get_kb_item('Host/cpu');
if (isnull(cpu)) audit(AUDIT_UNKNOWN_ARCH);
if ('x86_64' >!< cpu && cpu !~ "^i[3-6]86$") audit(AUDIT_LOCAL_CHECKS_NOT_IMPLEMENTED, 'Ubuntu', cpu);


pkgs = [
    {'osver': '16.04', 'pkgname': 'brotli', 'pkgver': '1.0.3-1ubuntu1~16.04.2'},
    {'osver': '16.04', 'pkgname': 'libbrotli-dev', 'pkgver': '1.0.3-1ubuntu1~16.04.2'},
    {'osver': '16.04', 'pkgname': 'libbrotli1', 'pkgver': '1.0.3-1ubuntu1~16.04.2'},
    {'osver': '16.04', 'pkgname': 'python-brotli', 'pkgver': '1.0.3-1ubuntu1~16.04.2'},
    {'osver': '16.04', 'pkgname': 'python3-brotli', 'pkgver': '1.0.3-1ubuntu1~16.04.2'},
    {'osver': '18.04', 'pkgname': 'brotli', 'pkgver': '1.0.3-1ubuntu1.3'},
    {'osver': '18.04', 'pkgname': 'libbrotli-dev', 'pkgver': '1.0.3-1ubuntu1.3'},
    {'osver': '18.04', 'pkgname': 'libbrotli1', 'pkgver': '1.0.3-1ubuntu1.3'},
    {'osver': '18.04', 'pkgname': 'python-brotli', 'pkgver': '1.0.3-1ubuntu1.3'},
    {'osver': '18.04', 'pkgname': 'python3-brotli', 'pkgver': '1.0.3-1ubuntu1.3'},
    {'osver': '20.04', 'pkgname': 'brotli', 'pkgver': '1.0.7-6ubuntu0.1'},
    {'osver': '20.04', 'pkgname': 'libbrotli-dev', 'pkgver': '1.0.7-6ubuntu0.1'},
    {'osver': '20.04', 'pkgname': 'libbrotli1', 'pkgver': '1.0.7-6ubuntu0.1'},
    {'osver': '20.04', 'pkgname': 'python3-brotli', 'pkgver': '1.0.7-6ubuntu0.1'}
];

flag = 0;
foreach package_array ( pkgs ) {
  osver = NULL;
  pkgname = NULL;
  pkgver = NULL;
  if (!empty_or_null(package_array['osver'])) osver = package_array['osver'];
  if (!empty_or_null(package_array['pkgname'])) pkgname = package_array['pkgname'];
  if (!empty_or_null(package_array['pkgver'])) pkgver = package_array['pkgver'];
  if (osver && pkgname && pkgver) {
    if (ubuntu_check(osver:osver, pkgname:pkgname, pkgver:pkgver)) flag++;
  }
}

if (flag)
{
  security_report_v4(
    port       : 0,
    severity   : SECURITY_WARNING,
    extra      : ubuntu_report_get()
  );
  exit(0);
}
else
{
  tested = ubuntu_pkg_tests_get();
  if (tested) audit(AUDIT_PACKAGE_NOT_AFFECTED, tested);
  else audit(AUDIT_PACKAGE_NOT_INSTALLED, 'brotli / libbrotli-dev / libbrotli1 / python-brotli / python3-brotli');
}

The latest version of this script can be found in these locations depending on your platform:

Linux / Unix:
/opt/nessus/lib/nessus/plugins/ubuntu_USN-4568-1.nasl
Windows:
C:\ProgramData\Tenable\Nessus\nessus\plugins\ubuntu_USN-4568-1.nasl
Mac OS X:
/Library/Nessus/run/lib/nessus/plugins/ubuntu_USN-4568-1.nasl

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How to Run

Here is how to run the Ubuntu 16.04 LTS / 18.04 LTS / 20.04 LTS : Brotli vulnerability (USN-4568-1) as a standalone plugin via the Nessus web user interface (https://localhost:8834/):

Click to start a New Scan.
Select Advanced Scan.
Navigate to the Plugins tab.
On the top right corner click to Disable All plugins.
On the left side table select Ubuntu Local Security Checks plugin family.
On the right side table select Ubuntu 16.04 LTS / 18.04 LTS / 20.04 LTS : Brotli vulnerability (USN-4568-1) plugin ID 141179.
Specify the target on the Settings tab and click to Save the scan.
Run the scan.

Here are a few examples of how to run the plugin in the command line. Note that the examples below demonstrate the usage on the Linux / Unix platform.

Basic usage:

/opt/nessus/bin/nasl ubuntu_USN-4568-1.nasl -t <IP/HOST>

Run the plugin with audit trail message on the console:

/opt/nessus/bin/nasl -a ubuntu_USN-4568-1.nasl -t <IP/HOST>

Run the plugin with trace script execution written to the console (useful for debugging):

/opt/nessus/bin/nasl -T - ubuntu_USN-4568-1.nasl -t <IP/HOST>

Run the plugin with using a state file for the target and updating it (useful for running multiple plugins on the target):

/opt/nessus/bin/nasl -K /tmp/state ubuntu_USN-4568-1.nasl -t <IP/HOST>

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References

USN | Ubuntu Security Notice:

4568-1

See also:

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Version

This page has been produced using Nessus Professional 10.1.2 (#68) LINUX, Plugin set 202205072148.
Plugin file ubuntu_USN-4568-1.nasl version 1.2. For more plugins, visit the Nessus Plugin Library.

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Ubuntu 16.04 LTS / 18.04 LTS / 20.04 LTS : Brotli vulnerability (USN-4568-1) - Nessus

Plugin Overview

Vulnerability Information

Synopsis

Description

Solution

Public Exploits

Risk Information

Plugin Source

How to Run

References

Version

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