CVSS2
Attack Vector
ADJACENT_NETWORK
Attack Complexity
LOW
Authentication
NONE
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
PARTIAL
AV:A/AC:L/Au:N/C:N/I:N/A:P
CVSS3
Attack Vector
ADJACENT
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
CHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
HIGH
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
AI Score
Confidence
High
EPSS
Percentile
68.3%
The version of dhcp installed on the remote host is prior to 4.1.1-53.P1.29. It is, therefore, affected by a vulnerability as referenced in the ALAS-2021-1510 advisory.
Note that Nessus has not tested for this issue but has instead relied only on the application’s self-reported version number.
#%NASL_MIN_LEVEL 70300
##
# (C) Tenable Network Security, Inc.
#
# The descriptive text and package checks in this plugin were
# extracted from Amazon Linux AMI Security Advisory ALAS-2021-1510.
##
include('deprecated_nasl_level.inc');
include('compat.inc');
if (description)
{
script_id(151509);
script_version("1.4");
script_set_attribute(attribute:"plugin_modification_date", value:"2023/12/08");
script_cve_id("CVE-2021-25217");
script_xref(name:"IAVB", value:"2021-B-0032-S");
script_xref(name:"ALAS", value:"2021-1510");
script_name(english:"Amazon Linux AMI : dhcp (ALAS-2021-1510)");
script_set_attribute(attribute:"synopsis", value:
"The remote Amazon Linux AMI host is missing a security update.");
script_set_attribute(attribute:"description", value:
"The version of dhcp installed on the remote host is prior to 4.1.1-53.P1.29. It is, therefore, affected by a
vulnerability as referenced in the ALAS-2021-1510 advisory.
- In ISC DHCP 4.1-ESV-R1 -> 4.1-ESV-R16, ISC DHCP 4.4.0 -> 4.4.2 (Other branches of ISC DHCP (i.e., releases
in the 4.0.x series or lower and releases in the 4.3.x series) are beyond their End-of-Life (EOL) and no
longer supported by ISC. From inspection it is clear that the defect is also present in releases from
those series, but they have not been officially tested for the vulnerability), The outcome of encountering
the defect while reading a lease that will trigger it varies, according to: the component being affected
(i.e., dhclient or dhcpd) whether the package was built as a 32-bit or 64-bit binary whether the compiler
flag -fstack-protection-strong was used when compiling In dhclient, ISC has not successfully reproduced
the error on a 64-bit system. However, on a 32-bit system it is possible to cause dhclient to crash when
reading an improper lease, which could cause network connectivity problems for an affected system due to
the absence of a running DHCP client process. In dhcpd, when run in DHCPv4 or DHCPv6 mode: if the dhcpd
server binary was built for a 32-bit architecture AND the -fstack-protection-strong flag was specified to
the compiler, dhcpd may exit while parsing a lease file containing an objectionable lease, resulting in
lack of service to clients. Additionally, the offending lease and the lease immediately following it in
the lease database may be improperly deleted. if the dhcpd server binary was built for a 64-bit
architecture OR if the -fstack-protection-strong compiler flag was NOT specified, the crash will not
occur, but it is possible for the offending lease and the lease which immediately followed it to be
improperly deleted. (CVE-2021-25217)
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://alas.aws.amazon.com/ALAS-2021-1510.html");
script_set_attribute(attribute:"see_also", value:"https://access.redhat.com/security/cve/CVE-2021-25217");
script_set_attribute(attribute:"solution", value:
"Run 'yum update dhcp' to update your system.");
script_set_cvss_base_vector("CVSS2#AV:A/AC:L/Au:N/C:N/I:N/A:P");
script_set_cvss_temporal_vector("CVSS2#E:POC/RL:OF/RC:C");
script_set_cvss3_base_vector("CVSS:3.0/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H");
script_set_cvss3_temporal_vector("CVSS:3.0/E:P/RL:O/RC:C");
script_set_attribute(attribute:"cvss_score_source", value:"CVE-2021-25217");
script_set_attribute(attribute:"exploitability_ease", value:"Exploits are available");
script_set_attribute(attribute:"exploit_available", value:"true");
script_set_attribute(attribute:"vuln_publication_date", value:"2021/05/26");
script_set_attribute(attribute:"patch_publication_date", value:"2021/07/08");
script_set_attribute(attribute:"plugin_publication_date", value:"2021/07/13");
script_set_attribute(attribute:"plugin_type", value:"local");
script_set_attribute(attribute:"cpe", value:"p-cpe:/a:amazon:linux:dhclient");
script_set_attribute(attribute:"cpe", value:"p-cpe:/a:amazon:linux:dhcp");
script_set_attribute(attribute:"cpe", value:"p-cpe:/a:amazon:linux:dhcp-common");
script_set_attribute(attribute:"cpe", value:"p-cpe:/a:amazon:linux:dhcp-debuginfo");
script_set_attribute(attribute:"cpe", value:"p-cpe:/a:amazon:linux:dhcp-devel");
script_set_attribute(attribute:"cpe", value:"cpe:/o:amazon:linux");
script_set_attribute(attribute:"stig_severity", value:"I");
script_end_attributes();
script_category(ACT_GATHER_INFO);
script_family(english:"Amazon Linux Local Security Checks");
script_copyright(english:"This script is Copyright (C) 2021-2023 and is owned by Tenable, Inc. or an Affiliate thereof.");
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);
pkgs = [
{'reference':'dhclient-4.1.1-53.P1.29.amzn1', 'cpu':'i686', 'release':'ALA', 'rpm_spec_vers_cmp':TRUE},
{'reference':'dhclient-4.1.1-53.P1.29.amzn1', 'cpu':'x86_64', 'release':'ALA', 'rpm_spec_vers_cmp':TRUE},
{'reference':'dhcp-4.1.1-53.P1.29.amzn1', 'cpu':'i686', 'release':'ALA', 'rpm_spec_vers_cmp':TRUE},
{'reference':'dhcp-4.1.1-53.P1.29.amzn1', 'cpu':'x86_64', 'release':'ALA', 'rpm_spec_vers_cmp':TRUE},
{'reference':'dhcp-common-4.1.1-53.P1.29.amzn1', 'cpu':'i686', 'release':'ALA', 'rpm_spec_vers_cmp':TRUE},
{'reference':'dhcp-common-4.1.1-53.P1.29.amzn1', 'cpu':'x86_64', 'release':'ALA', 'rpm_spec_vers_cmp':TRUE},
{'reference':'dhcp-debuginfo-4.1.1-53.P1.29.amzn1', 'cpu':'i686', 'release':'ALA', 'rpm_spec_vers_cmp':TRUE},
{'reference':'dhcp-debuginfo-4.1.1-53.P1.29.amzn1', 'cpu':'x86_64', 'release':'ALA', 'rpm_spec_vers_cmp':TRUE},
{'reference':'dhcp-devel-4.1.1-53.P1.29.amzn1', 'cpu':'i686', 'release':'ALA', 'rpm_spec_vers_cmp':TRUE},
{'reference':'dhcp-devel-4.1.1-53.P1.29.amzn1', 'cpu':'x86_64', 'release':'ALA', 'rpm_spec_vers_cmp':TRUE}
];
flag = 0;
foreach package_array ( pkgs ) {
reference = NULL;
release = NULL;
cpu = NULL;
el_string = NULL;
rpm_spec_vers_cmp = NULL;
allowmaj = NULL;
if (!empty_or_null(package_array['reference'])) reference = package_array['reference'];
if (!empty_or_null(package_array['release'])) release = package_array['release'];
if (!empty_or_null(package_array['cpu'])) cpu = package_array['cpu'];
if (!empty_or_null(package_array['el_string'])) el_string = package_array['el_string'];
if (!empty_or_null(package_array['rpm_spec_vers_cmp'])) rpm_spec_vers_cmp = package_array['rpm_spec_vers_cmp'];
if (!empty_or_null(package_array['allowmaj'])) allowmaj = package_array['allowmaj'];
if (reference && release) {
if (rpm_check(release:release, cpu:cpu, reference:reference, el_string:el_string, rpm_spec_vers_cmp:rpm_spec_vers_cmp, allowmaj:allowmaj)) flag++;
}
}
if (flag)
{
security_report_v4(
port : 0,
severity : SECURITY_NOTE,
extra : rpm_report_get()
);
exit(0);
}
else
{
tested = pkg_tests_get();
if (tested) audit(AUDIT_PACKAGE_NOT_AFFECTED, tested);
else audit(AUDIT_PACKAGE_NOT_INSTALLED, "dhclient / dhcp / dhcp-common / etc");
}
CVSS2
Attack Vector
ADJACENT_NETWORK
Attack Complexity
LOW
Authentication
NONE
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
PARTIAL
AV:A/AC:L/Au:N/C:N/I:N/A:P
CVSS3
Attack Vector
ADJACENT
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
CHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
HIGH
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
AI Score
Confidence
High
EPSS
Percentile
68.3%