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

2015-07-24T00:00:00
ID ALA_ALAS-2015-572.NASL
Type nessus
Reporter This script is Copyright (C) 2015-2018 Tenable Network Security, Inc.
Modified 2021-06-02T00:00:00

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)

                                        
                                            #
# (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");
}