7.2 High
CVSS2
Attack Vector
LOCAL
Attack Complexity
LOW
Authentication
NONE
Confidentiality Impact
COMPLETE
Integrity Impact
COMPLETE
Availability Impact
COMPLETE
AV:L/AC:L/Au:N/C:C/I:C/A:C
8.8 High
CVSS3
Attack Vector
LOCAL
Attack Complexity
LOW
Privileges Required
LOW
User Interaction
NONE
Scope
CHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
8.2 High
AI Score
Confidence
High
0.006 Low
EPSS
Percentile
78.3%
The remote Ubuntu 20.04 LTS host has a package installed that is affected by multiple vulnerabilities as referenced in the USN-4915-1 advisory.
Shiftfs, an out-of-tree stacking file system included in Ubuntu Linux kernels, did not properly handle faults occurring during copy_from_user() correctly. These could lead to either a double-free situation or memory not being freed at all. An attacker could use this to cause a denial of service (kernel memory exhaustion) or gain privileges via executing arbitrary code. AKA ZDI-CAN-13562. (CVE-2021-3492)
The overlayfs implementation in the linux kernel did not properly validate with respect to user namespaces the setting of file capabilities on files in an underlying file system. Due to the combination of unprivileged user namespaces along with a patch carried in the Ubuntu kernel to allow unprivileged overlay mounts, an attacker could use this to gain elevated privileges. (CVE-2021-3493)
Note that Nessus has not tested for these issues but has instead relied only on the applicationโs self-reported version number.
##
# (C) Tenable Network Security, Inc.
#
# The descriptive text and package checks in this plugin were
# extracted from Ubuntu Security Notice USN-4915-1. The text
# itself is copyright (C) Canonical, Inc. See
# <https://ubuntu.com/security/notices>. Ubuntu(R) is a registered
# trademark of Canonical, Inc.
##
include('compat.inc');
if (description)
{
script_id(148689);
script_version("1.12");
script_set_attribute(attribute:"plugin_modification_date", value:"2024/01/09");
script_cve_id("CVE-2021-3492", "CVE-2021-3493");
script_xref(name:"USN", value:"4915-1");
script_xref(name:"CISA-KNOWN-EXPLOITED", value:"2022/11/10");
script_name(english:"Ubuntu 20.04 LTS : Linux kernel (OEM) vulnerabilities (USN-4915-1)");
script_set_attribute(attribute:"synopsis", value:
"The remote Ubuntu host is missing one or more security updates.");
script_set_attribute(attribute:"description", value:
"The remote Ubuntu 20.04 LTS host has a package installed that is affected by multiple vulnerabilities as referenced in
the USN-4915-1 advisory.
- Shiftfs, an out-of-tree stacking file system included in Ubuntu Linux kernels, did not properly handle
faults occurring during copy_from_user() correctly. These could lead to either a double-free situation or
memory not being freed at all. An attacker could use this to cause a denial of service (kernel memory
exhaustion) or gain privileges via executing arbitrary code. AKA ZDI-CAN-13562. (CVE-2021-3492)
- The overlayfs implementation in the linux kernel did not properly validate with respect to user namespaces
the setting of file capabilities on files in an underlying file system. Due to the combination of
unprivileged user namespaces along with a patch carried in the Ubuntu kernel to allow unprivileged overlay
mounts, an attacker could use this to gain elevated privileges. (CVE-2021-3493)
Note that Nessus has not tested for these issues 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-4915-1");
script_set_attribute(attribute:"solution", value:
"Update the affected kernel package.");
script_set_cvss_base_vector("CVSS2#AV:L/AC:L/Au:N/C:C/I:C/A:C");
script_set_cvss_temporal_vector("CVSS2#E:H/RL:OF/RC:C");
script_set_cvss3_base_vector("CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H");
script_set_cvss3_temporal_vector("CVSS:3.0/E:H/RL:O/RC:C");
script_set_attribute(attribute:"cvss_score_source", value:"CVE-2021-3493");
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:'2021 Ubuntu Overlayfs LPE');
script_set_attribute(attribute:"exploit_framework_metasploit", value:"true");
script_set_attribute(attribute:"exploit_framework_canvas", value:"true");
script_set_attribute(attribute:"canvas_package", value:"CANVAS");
script_set_attribute(attribute:"vuln_publication_date", value:"2021/04/15");
script_set_attribute(attribute:"patch_publication_date", value:"2021/04/15");
script_set_attribute(attribute:"plugin_publication_date", value:"2021/04/16");
script_set_attribute(attribute:"plugin_type", value:"local");
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:linux-image-5.6.0-1054-oem");
script_set_attribute(attribute:"generated_plugin", value:"current");
script_end_attributes();
script_category(ACT_GATHER_INFO);
script_family(english:"Ubuntu Local Security Checks");
script_copyright(english:"Ubuntu Security Notice (C) 2021-2024 Canonical, Inc. / NASL script (C) 2021-2024 and is owned by Tenable, Inc. or an Affiliate thereof.");
script_dependencies("ssh_get_info.nasl", "linux_alt_patch_detect.nasl");
script_require_keys("Host/cpu", "Host/Ubuntu", "Host/Ubuntu/release", "Host/Debian/dpkg-l");
exit(0);
}
include('debian_package.inc');
include('ksplice.inc');
if ( ! get_kb_item('Host/local_checks_enabled') ) audit(AUDIT_LOCAL_CHECKS_NOT_ENABLED);
var os_release = get_kb_item('Host/Ubuntu/release');
if ( isnull(os_release) ) audit(AUDIT_OS_NOT, 'Ubuntu');
os_release = chomp(os_release);
if (! ('20.04' >< os_release)) audit(AUDIT_OS_NOT, 'Ubuntu 20.04', 'Ubuntu ' + os_release);
if ( ! get_kb_item('Host/Debian/dpkg-l') ) audit(AUDIT_PACKAGE_LIST_MISSING);
var cpu = get_kb_item('Host/cpu');
if (isnull(cpu)) audit(AUDIT_UNKNOWN_ARCH);
if ('x86_64' >!< cpu && cpu !~ "^i[3-6]86$" && 's390' >!< cpu && 'aarch64' >!< cpu) audit(AUDIT_LOCAL_CHECKS_NOT_IMPLEMENTED, 'Ubuntu', cpu);
var kernel_mappings = {
'20.04': {
'5.6.0': {
'oem': '5.6.0-1054'
}
}
};
var host_kernel_release = get_kb_item('Host/uptrack-uname-r');
if (empty_or_null(host_kernel_release)) host_kernel_release = get_kb_item_or_exit('Host/uname-r');
var host_kernel_base_version = get_kb_item_or_exit('Host/Debian/kernel-base-version');
var host_kernel_type = get_kb_item_or_exit('Host/Debian/kernel-type');
if(empty_or_null(kernel_mappings[os_release][host_kernel_base_version][host_kernel_type])) audit(AUDIT_INST_VER_NOT_VULN, 'kernel ' + host_kernel_release);
var extra = '';
var kernel_fixed_version = kernel_mappings[os_release][host_kernel_base_version][host_kernel_type] + "-" + host_kernel_type;
if (deb_ver_cmp(ver1:host_kernel_release, ver2:kernel_fixed_version) < 0)
{
extra = extra + 'Running Kernel level of ' + host_kernel_release + ' does not meet the minimum fixed level of ' + kernel_fixed_version + ' for this advisory.\n\n';
}
else
{
audit(AUDIT_PATCH_INSTALLED, 'Kernel package for USN-4915-1');
}
if (get_one_kb_item('Host/ksplice/kernel-cves'))
{
var cve_list = make_list('CVE-2021-3492', 'CVE-2021-3493');
if (ksplice_cves_check(cve_list))
{
audit(AUDIT_PATCH_INSTALLED, 'KSplice hotfix for USN-4915-1');
}
else
{
extra = extra + ksplice_reporting_text();
}
}
if (extra) {
security_report_v4(
port : 0,
severity : SECURITY_HOLE,
extra : extra
);
exit(0);
}
Vendor | Product | Version | CPE |
---|---|---|---|
canonical | ubuntu_linux | 20.04 | cpe:/o:canonical:ubuntu_linux:20.04:-:lts |
canonical | ubuntu_linux | linux-image-5.6.0-1054-oem | p-cpe:/a:canonical:ubuntu_linux:linux-image-5.6.0-1054-oem |
7.2 High
CVSS2
Attack Vector
LOCAL
Attack Complexity
LOW
Authentication
NONE
Confidentiality Impact
COMPLETE
Integrity Impact
COMPLETE
Availability Impact
COMPLETE
AV:L/AC:L/Au:N/C:C/I:C/A:C
8.8 High
CVSS3
Attack Vector
LOCAL
Attack Complexity
LOW
Privileges Required
LOW
User Interaction
NONE
Scope
CHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
8.2 High
AI Score
Confidence
High
0.006 Low
EPSS
Percentile
78.3%