Amazon Linux AMI : usermode / libuser (ALAS-2015-572) - Nessus

High Plugin ID: 84964

This page contains detailed information about the Amazon Linux AMI : usermode / libuser (ALAS-2015-572) 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: 84964
Name: Amazon Linux AMI : usermode / libuser (ALAS-2015-572)
Filename: ala_ALAS-2015-572.nasl
Vulnerability Published: N/A
This Plugin Published: 2015-07-24
Last Modification Time: 2018-05-15
Plugin Version: 2.13
Plugin Type: local
Plugin Family: Amazon Linux Local Security Checks
Dependencies: ssh_get_info.nasl
Required KB Items [?]: Host/AmazonLinux/release, Host/AmazonLinux/rpm-list, Host/local_checks_enabled

Vulnerability Information

Severity: High
Vulnerability Published: N/A
Patch Published: 2015-07-23
CVE [?]: CVE-2015-3245, CVE-2015-3246
CPE [?]: cpe:/o:amazon:linux, p-cpe:/a:amazon:linux:libuser, p-cpe:/a:amazon:linux:libuser-debuginfo, p-cpe:/a:amazon:linux:libuser-devel, p-cpe:/a:amazon:linux:libuser-python, p-cpe:/a:amazon:linux:usermode, p-cpe:/a:amazon:linux:usermode-debuginfo
Exploited by Malware: True

Synopsis

The remote Amazon Linux AMI host is missing a security update.

Description

It was found that libuser, as used in the chfn userhelper functionality, does not properly filter out newline characters, which allows an authenticated local attacker to corrupt the /etc/passwd file and cause denial-of-service against the system. (CVE-2015-3245)

A flaw was found in the way the libuser library handled the /etc/passwd file. A local attacker could use an application compiled against libuser (for example, userhelper) to manipulate the /etc/passwd file, which could result in a denial of service or possibly allow the attacker to escalate their privileges to root. (CVE-2015-3246)

Solution

Run 'yum update usermode libuser' to update your system.

Public Exploits

Target Network Port(s): N/A
Target Asset(s): N/A
Exploit Available: True (Metasploit Framework, Exploit-DB, GitHub, Core Impact)
Exploit Ease: Exploits are available

Here's the list of publicly known exploits and PoCs for verifying the Amazon Linux AMI : usermode / libuser (ALAS-2015-572) vulnerability:

Metasploit: exploit/linux/local/libuser_roothelper_priv_esc
[Libuser roothelper Privilege Escalation]
Exploit-DB: exploits/linux/dos/37706.txt
[EDB-37706: Libuser Library - Multiple Vulnerabilities]
Exploit-DB: exploits/linux/local/44633.rb
[EDB-44633: Libuser - 'roothelper' Local Privilege Escalation (Metasploit)]
GitHub: https://github.com/ARGOeu/secmon-probes
[CVE-2015-3245]

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 V2 Vector [?]: AV:L/AC:L/Au:N/C:C/I:C/A:C

CVSS Base Score:	7.2 (High)
Impact Subscore:	10.0
Exploitability Subscore:	3.9
CVSS Temporal Score:	NA (None)
CVSS Environmental Score:	NA (None)
Modified Impact Subscore:	NA
Overall CVSS Score:	7.2 (High)

STIG Severity [?]: I
STIG Risk Rating: High

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Plugin Source

#
# (C) Tenable Network Security, Inc.
#
# The descriptive text and package checks in this plugin were
# extracted from Amazon Linux AMI Security Advisory ALAS-2015-572.
#

include("compat.inc");

if (description)
{
  script_id(84964);
  script_version("2.13");
  script_cvs_date("Date: 2018/05/15 11:39:34");

  script_cve_id("CVE-2015-3245", "CVE-2015-3246");
  script_xref(name:"ALAS", value:"2015-572");
  script_xref(name:"IAVA", value:"2015-A-0179");
  script_xref(name:"RHSA", value:"2015:1482");

  script_name(english:"Amazon Linux AMI : usermode / libuser (ALAS-2015-572)");
  script_summary(english:"Checks rpm output for the updated packages");

  script_set_attribute(
    attribute:"synopsis", 
    value:"The remote Amazon Linux AMI host is missing a security update."
  );
  script_set_attribute(
    attribute:"description", 
    value:
"It was found that libuser, as used in the chfn userhelper
functionality, does not properly filter out newline characters, which
allows an authenticated local attacker to corrupt the /etc/passwd file
and cause denial-of-service against the system. (CVE-2015-3245)

A flaw was found in the way the libuser library handled the
/etc/passwd file. A local attacker could use an application compiled
against libuser (for example, userhelper) to manipulate the
/etc/passwd file, which could result in a denial of service or
possibly allow the attacker to escalate their privileges to root.
(CVE-2015-3246)"
  );
  script_set_attribute(
    attribute:"see_also",
    value:"https://alas.aws.amazon.com/ALAS-2015-572.html"
  );
  script_set_attribute(
    attribute:"solution", 
    value:"Run 'yum update usermode libuser' to update your system."
  );
  script_set_cvss_base_vector("CVSS2#AV:L/AC:L/Au:N/C:C/I:C/A:C");
  script_set_attribute(attribute:"exploitability_ease", value:"Exploits are available");
  script_set_attribute(attribute:"exploit_available", value:"true");
  script_set_attribute(attribute:"exploit_framework_core", value:"true");
  script_set_attribute(attribute:"exploited_by_malware", value:"true");
  script_set_attribute(attribute:"metasploit_name", value:'Libuser roothelper Privilege Escalation');
  script_set_attribute(attribute:"exploit_framework_metasploit", value:"true");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:amazon:linux:libuser");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:amazon:linux:libuser-debuginfo");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:amazon:linux:libuser-devel");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:amazon:linux:libuser-python");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:amazon:linux:usermode");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:amazon:linux:usermode-debuginfo");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:amazon:linux");

  script_set_attribute(attribute:"patch_publication_date", value:"2015/07/23");
  script_set_attribute(attribute:"plugin_publication_date", value:"2015/07/24");
  script_set_attribute(attribute:"stig_severity", value:"I");
  script_end_attributes();

  script_category(ACT_GATHER_INFO);
  script_copyright(english:"This script is Copyright (C) 2015-2018 Tenable Network Security, Inc.");
  script_family(english:"Amazon Linux Local Security Checks");

  script_dependencies("ssh_get_info.nasl");
  script_require_keys("Host/local_checks_enabled", "Host/AmazonLinux/release", "Host/AmazonLinux/rpm-list");

  exit(0);
}


include("audit.inc");
include("global_settings.inc");
include("rpm.inc");


if (!get_kb_item("Host/local_checks_enabled")) audit(AUDIT_LOCAL_CHECKS_NOT_ENABLED);

release = get_kb_item("Host/AmazonLinux/release");
if (isnull(release) || !strlen(release)) audit(AUDIT_OS_NOT, "Amazon Linux");
os_ver = pregmatch(pattern: "^AL(A|\d)", string:release);
if (isnull(os_ver)) audit(AUDIT_UNKNOWN_APP_VER, "Amazon Linux");
os_ver = os_ver[1];
if (os_ver != "A")
{
  if (os_ver == 'A') os_ver = 'AMI';
  audit(AUDIT_OS_NOT, "Amazon Linux AMI", "Amazon Linux " + os_ver);
}

if (!get_kb_item("Host/AmazonLinux/rpm-list")) audit(AUDIT_PACKAGE_LIST_MISSING);


flag = 0;
if (rpm_check(release:"ALA", reference:"libuser-0.56.13-8.15.amzn1")) flag++;
if (rpm_check(release:"ALA", reference:"libuser-debuginfo-0.56.13-8.15.amzn1")) flag++;
if (rpm_check(release:"ALA", reference:"libuser-devel-0.56.13-8.15.amzn1")) flag++;
if (rpm_check(release:"ALA", reference:"libuser-python-0.56.13-8.15.amzn1")) flag++;
if (rpm_check(release:"ALA", reference:"usermode-1.102-3.18.amzn1")) flag++;
if (rpm_check(release:"ALA", reference:"usermode-debuginfo-1.102-3.18.amzn1")) flag++;

if (flag)
{
  if (report_verbosity > 0) security_hole(port:0, extra:rpm_report_get());
  else security_hole(0);
  exit(0);
}
else
{
  tested = pkg_tests_get();
  if (tested) audit(AUDIT_PACKAGE_NOT_AFFECTED, tested);
  else audit(AUDIT_PACKAGE_NOT_INSTALLED, "libuser / libuser-debuginfo / libuser-devel / libuser-python / etc");
}

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

Linux / Unix:
/opt/nessus/lib/nessus/plugins/ala_ALAS-2015-572.nasl
Windows:
C:\ProgramData\Tenable\Nessus\nessus\plugins\ala_ALAS-2015-572.nasl
Mac OS X:
/Library/Nessus/run/lib/nessus/plugins/ala_ALAS-2015-572.nasl

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How to Run

Here is how to run the Amazon Linux AMI : usermode / libuser (ALAS-2015-572) 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 Amazon Linux Local Security Checks plugin family.
On the right side table select Amazon Linux AMI : usermode / libuser (ALAS-2015-572) plugin ID 84964.
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 ala_ALAS-2015-572.nasl -t <IP/HOST>

Run the plugin with audit trail message on the console:

/opt/nessus/bin/nasl -a ala_ALAS-2015-572.nasl -t <IP/HOST>

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

/opt/nessus/bin/nasl -T - ala_ALAS-2015-572.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 ala_ALAS-2015-572.nasl -t <IP/HOST>

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References

RHSA | Red Hat Security Advisory:

2015:1482

IAVA | Information Assurance Vulnerability Alert:

2015-A-0179

ALAS | Amazon Linux Security Advisory:

2015-572

See also:

Similar and related Nessus plugins:

85029 - CentOS 6 : libuser (CESA-2015:1482)
84988 - CentOS 7 : libuser (CESA-2015:1483)
91108 - Debian DLA-468-1 : libuser security update
91327 - F5 Networks BIG-IP : Linux libuser vulnerability (SOL05770600)
85167 - Fedora 21 : libuser-0.62-1.fc21 (2015-12064)
85134 - Fedora 22 : libuser-0.62-1.fc22 (2015-12301)
147366 - NewStart CGSL CORE 5.04 / MAIN 5.04 : libuser Multiple Vulnerabilities (NS-SA-2021-0044)
85186 - openSUSE Security Update : libuser (openSUSE-2015-529)
85115 - Oracle Linux 6 : libuser (ELSA-2015-1482)
84975 - Oracle Linux 7 : libuser (ELSA-2015-1483)
85147 - OracleVM 3.3 : libuser (OVMSA-2015-0106)
84976 - RHEL 6 : libuser (RHSA-2015:1482)
84977 - RHEL 7 : libuser (RHSA-2015:1483)
85210 - Scientific Linux Security Update : libuser on SL6.x i386/x86_64 (20150723)
85004 - Scientific Linux Security Update : libuser on SL7.x x86_64 (20150723)

Version

This page has been produced using Nessus Professional 10.1.2 (#68) LINUX, Plugin set 202205072148.
Plugin file ala_ALAS-2015-572.nasl version 2.13. For more plugins, visit the Nessus Plugin Library.

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Amazon Linux AMI : usermode / libuser (ALAS-2015-572) - Nessus

Plugin Overview

Vulnerability Information

Synopsis

Description

Solution

Public Exploits

Risk Information

Plugin Source

How to Run

References

Version

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