Amazon Linux 2 : zsh (ALAS-2018-1089)

2018-10-11T00:00:00
ID AL2_ALAS-2018-1089.NASL
Type nessus
Reporter Tenable
Modified 2018-10-29T00:00:00

Description

An issue was discovered in zsh before 5.6. The beginning of a #! script file was mishandled, potentially leading to an execve call to a program named on the second line.(CVE-2018-0502)

It was discovered that zsh does not properly validate the shebang of input files and it truncates it to the first 64 bytes. A local attacker may use this flaw to make zsh execute a different binary than what is expected, named with a substring of the shebang one.(CVE-2018-13259)

                                        
                                            #
# (C) Tenable Network Security, Inc.
#
# The descriptive text and package checks in this plugin were
# extracted from Amazon Linux 2 Security Advisory ALAS-2018-1089.
#

include("compat.inc");

if (description)
{
  script_id(118044);
  script_version("1.2");
  script_cvs_date("Date: 2018/10/29 10:22:57");

  script_cve_id("CVE-2018-0502", "CVE-2018-13259");
  script_xref(name:"ALAS", value:"2018-1089");

  script_name(english:"Amazon Linux 2 : zsh (ALAS-2018-1089)");
  script_summary(english:"Checks rpm output for the updated packages");

  script_set_attribute(
    attribute:"synopsis", 
    value:"The remote Amazon Linux 2 host is missing a security update."
  );
  script_set_attribute(
    attribute:"description", 
    value:
"An issue was discovered in zsh before 5.6. The beginning of a #!
script file was mishandled, potentially leading to an execve call to a
program named on the second line.(CVE-2018-0502)

It was discovered that zsh does not properly validate the shebang of
input files and it truncates it to the first 64 bytes. A local
attacker may use this flaw to make zsh execute a different binary than
what is expected, named with a substring of the shebang
one.(CVE-2018-13259)"
  );
  script_set_attribute(
    attribute:"see_also",
    value:"https://alas.aws.amazon.com/AL2/ALAS-2018-1089.html"
  );
  script_set_attribute(
    attribute:"solution", 
    value:"Run 'yum update zsh' to update your system."
  );
  script_set_cvss_base_vector("CVSS2#AV:N/AC:L/Au:N/C:P/I:P/A:P");
  script_set_cvss3_base_vector("CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:amazon:linux:zsh");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:amazon:linux:zsh-debuginfo");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:amazon:linux:zsh-html");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:amazon:linux:2");

  script_set_attribute(attribute:"patch_publication_date", value:"2018/10/10");
  script_set_attribute(attribute:"plugin_publication_date", value:"2018/10/11");
  script_end_attributes();

  script_category(ACT_GATHER_INFO);
  script_copyright(english:"This script is Copyright (C) 2018 and is owned by Tenable, Inc. or an Affiliate thereof.");
  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 != "2")
{
  if (os_ver == 'A') os_ver = 'AMI';
  audit(AUDIT_OS_NOT, "Amazon Linux 2", "Amazon Linux " + os_ver);
}

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


flag = 0;
if (rpm_check(release:"AL2", reference:"zsh-5.5.1-2.amzn2.0.1")) flag++;
if (rpm_check(release:"AL2", reference:"zsh-debuginfo-5.5.1-2.amzn2.0.1")) flag++;
if (rpm_check(release:"AL2", reference:"zsh-html-5.5.1-2.amzn2.0.1")) 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, "zsh / zsh-debuginfo / zsh-html");
}