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AUSCERT External Security Bulletin Redistribution
ESB-2021.1531
Cisco AnyConnect Secure Mobility Client for Windows DLL and
Executable Hijacking Vulnerabilities
6 May 2021
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AusCERT Security Bulletin Summary
---------------------------------
Product: Cisco AnyConnect
Publisher: Cisco Systems
Operating System: Windows
Impact/Access: Administrator Compromise -- Existing Account
Execute Arbitrary Code/Commands -- Existing Account
Resolution: Patch/Upgrade
CVE Names: CVE-2021-1496 CVE-2021-1430 CVE-2021-1429
CVE-2021-1428 CVE-2021-1427 CVE-2021-1426
Original Bulletin:
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-anyconnect-code-exec-jR3tWTA6
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Cisco AnyConnect Secure Mobility Client for Windows DLL and Executable
Hijacking Vulnerabilities
Priority: High
Advisory ID: cisco-sa-anyconnect-code-exec-jR3tWTA6
First Published: 2021 May 5 16:00 GMT
Version 1.0: Final
Workarounds: No workarounds available
Cisco Bug IDs: CSCvu77671 CSCvv43102 CSCvv60844 CSCvw16996 CSCvw17005
CSCvw18527 CSCvw18595
CVE Names: CVE-2021-1426 CVE-2021-1427 CVE-2021-1428 CVE-2021-1429
CVE-2021-1430 CVE-2021-1496
CWEs: CWE-378
Summary
o Multiple vulnerabilities in the install, uninstall, and upgrade processes
of Cisco AnyConnect Secure Mobility Client for Windows could allow an
authenticated, local attacker to hijack DLL or executable files that are
used by the application. A successful exploit could allow the attacker to
execute arbitrary code on an affected device with SYSTEM privileges. To
exploit these vulnerabilities, the attacker must have valid credentials on
the Windows system.
For more information about these vulnerabilities, see the Details section
of this advisory.
Cisco has released software updates that address these vulnerabilities.
There are no workarounds that address these vulnerabilities.
This advisory is available at the following link:
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-anyconnect-code-exec-jR3tWTA6
Affected Products
o Vulnerable Products
These vulnerabilities affect Cisco devices if they are running a vulnerable
release of Cisco AnyConnect Secure Mobility Client for Windows.
For information about which Cisco software releases are vulnerable, see the
Fixed Software section of this advisory.
Products Confirmed Not Vulnerable
Only products listed in the Vulnerable Products section of this advisory
are known to be affected by these vulnerabilities.
Cisco has confirmed that these vulnerabilities do not affect the following
Cisco products:
AnyConnect Secure Mobility Client for Linux
AnyConnect Secure Mobility Client for Mac OS
AnyConnect Secure Mobility Client for mobile device operating systems
such as iOS, Android, and Universal Windows Platform
Details
o The vulnerabilities are not dependent on one another. Exploitation of one
of the vulnerabilities is not required to exploit another vulnerability. In
addition, a software release that is affected by one of the vulnerabilities
may not be affected by the other vulnerabilities.
Details about the vulnerabilities are as follows.
Cisco AnyConnect Secure Mobility Client for Windows Uninstall Executable
Hijacking Vulnerability
A vulnerability in the uninstall process of Cisco AnyConnect Secure
Mobility Client for Windows could allow an authenticated, local attacker to
perform an executable hijacking attack on an affected device.
This vulnerability exists because a temporary file with insecure
permissions is created during the uninstall process. An attacker could
exploit this vulnerability by overwriting the temporary file before it is
accessed for execution. A successful exploit could allow the attacker to
execute arbitrary code on the affected device with SYSTEM privileges. To
exploit this vulnerability, the attacker must have valid credentials on the
Windows system.
Cisco has released software updates that address this vulnerability. There
are no workarounds that address this vulnerability.
Bug ID(s): CSCvv43102, CSCvv60844
CVE ID(s): CVE-2021-1426
Security Impact Rating (SIR): High
CVSS Base Score: 7.0
CVSS Vector: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Cisco AnyConnect Secure Mobility Client for Windows Upgrade DLL Hijacking
Vulnerabilities
Two vulnerabilities in the upgrade process of Cisco AnyConnect Secure
Mobility Client for Windows could allow an authenticated, local attacker to
perform a DLL hijacking attack on an affected device.
These vulnerabilities exist because the application loads a DLL file from a
user-writable directory. An attacker could exploit these vulnerabilities by
copying a malicious DLL file to a specific directory. A successful exploit
could allow the attacker to execute arbitrary code on the affected device
with SYSTEM privileges. To exploit these vulnerabilities, the attacker must
have valid credentials on the Windows system.
Cisco has released software updates that address these vulnerabilities.
There are no workarounds that address these vulnerabilities.
Bug ID(s): CSCvw16996, CSCvw17005
CVE ID(s): CVE-2021-1427, CVE-2021-1428
Security Impact Rating (SIR): High
CVSS Base Score: 7.0
CVSS Vector: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Cisco AnyConnect Secure Mobility Client for Windows Upgrade Executable
Hijacking Vulnerability
A vulnerability in the install process of Cisco AnyConnect Secure Mobility
Client for Windows could allow an authenticated, local attacker to perform
an executable hijacking attack on an affected device.
This vulnerability exists because a temporary file with insecure
permissions is created during the upgrade process. An attacker could
exploit this vulnerability by overwriting the temporary file before it is
accessed for execution. A successful exploit could allow the attacker to
execute arbitrary code on the affected device with SYSTEM privileges. To
exploit this vulnerability, the attacker must have valid credentials on the
Windows system.
Cisco has released software updates that address this vulnerability. There
are no workarounds that address this vulnerability.
Bug ID(s): CSCvw18527
CVE ID(s): CVE-2021-1429
Security Impact Rating (SIR): High
CVSS Base Score: 7.0
CVSS Vector: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Cisco AnyConnect Secure Mobility Client for Windows Upgrade DLL Hijacking
Vulnerability
A vulnerability in the upgrade process of Cisco AnyConnect Secure Mobility
Client for Windows could allow an authenticated, local attacker to perform
a DLL hijacking attack on an affected device.
This vulnerability exists because a temporary file with insecure
permissions is created during the upgrade process. An attacker could
exploit this vulnerability by overwriting the temporary file before it is
accessed for execution. A successful exploit could allow the attacker to
execute arbitrary code on the affected device with SYSTEM privileges. To
exploit this vulnerability, the attacker must have valid credentials on the
Windows system.
Cisco has released software updates that address this vulnerability. There
are no workarounds that address this vulnerability.
Bug ID(s): CSCvw18595
CVE ID(s): CVE-2021-1430
Security Impact Rating (SIR): High
CVSS Base Score: 7.0
CVSS Vector: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Cisco AnyConnect Secure Mobility Client for Windows Install Executable
Hijacking Vulnerability
A vulnerability in the install process of Cisco AnyConnect Secure Mobility
Client for Windows could allow an authenticated, local attacker to perform
an executable hijacking attack on an affected device.
This vulnerability exists because the application loads an executable file
from a user-writable directory. An attacker could exploit this
vulnerability by copying a malicious executable file to a specific
directory, which would be executed when the application is installed or
upgraded. A successful exploit could allow the attacker to execute
arbitrary code on the affected device with SYSTEM privileges. To exploit
this vulnerability, the attacker needs valid credentials on the Windows
system.
Cisco has released software updates that address this vulnerability. There
are no workarounds that address this vulnerability.
Bug ID(s): CSCvu77671
CVE ID(s): CVE-2021-1496
Security Impact Rating (SIR): High
CVSS Base Score: 7.0
CVSS Vector: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Workarounds
o There are no workarounds that address these vulnerabilities.
Fixed Software
o Cisco has released free software updates that address the vulnerabilities
described in this advisory. Customers may only install and expect support
for software versions and feature sets for which they have purchased a
license. By installing, downloading, accessing, or otherwise using such
software upgrades, customers agree to follow the terms of the Cisco
software license:
https://www.cisco.com/c/en/us/products/end-user-license-agreement.html
Additionally, customers may only download software for which they have a
valid license, procured from Cisco directly, or through a Cisco authorized
reseller or partner. In most cases this will be a maintenance upgrade to
software that was previously purchased. Free security software updates do
not entitle customers to a new software license, additional software
feature sets, or major revision upgrades.
When considering software upgrades , customers are advised to regularly
consult the advisories for Cisco products, which are available from the
Cisco Security Advisories page , to determine exposure and a complete
upgrade solution.
In all cases, customers should ensure that the devices to be upgraded
contain sufficient memory and confirm that current hardware and software
configurations will continue to be supported properly by the new release.
If the information is not clear, customers are advised to contact the Cisco
Technical Assistance Center (TAC) or their contracted maintenance
providers.
Customers Without Service Contracts
Customers who purchase directly from Cisco but do not hold a Cisco service
contract and customers who make purchases through third-party vendors but
are unsuccessful in obtaining fixed software through their point of sale
should obtain upgrades by contacting the Cisco TAC: https://www.cisco.com/c
/en/us/support/web/tsd-cisco-worldwide-contacts.html
Customers should have the product serial number available and be prepared
to provide the URL of this advisory as evidence of entitlement to a free
upgrade.
Fixed Releases
In the following table, the left column lists the CVE identifiers for the
vulnerabilities that are addressed in this advisory. The center column
indicates which software releases are affected by the vulnerability. The
right column lists the first release that includes the fix for that
vulnerability. Customers are advised to upgrade to an appropriate fixed
software release as indicated in this section.
CVE Affected Releases of Cisco First Fixed Release for This
Identifiers AnyConnect Vulnerability
Secure Mobility Client for
Windows
CVE-2021-1426 Earlier than 4.9.06037 4.9.06037
CVE-2021-1427 Earlier than 4.9.06037 4.9.06037
CVE-2021-1428 Earlier than 4.10.00093 4.10.00093
CVE-2021-1429 Earlier than 4.10.00093 4.10.00093
CVE-2021-1430 Earlier than 4.9.06037 4.9.06037
CVE-2021-1496 Earlier than 4.9.03022 4.9.03022
To download the software from the Software Center on Cisco.com, do the
following:
1. Click Browse all .
2. Choose Security > VPN and Endpoint Security Clients > Cisco VPN Clients
> AnyConnect Secure Mobility Client > AnyConnect Secure Mobility Client
v4.x .
3. Choose a release from the left pane of the AnyConnect Secure Mobility
Client v4.x page.
Exploitation and Public Announcements
o The Cisco Product Security Incident Response Team (PSIRT) is not aware of
any public announcements or malicious use of the vulnerabilities that are
described in this advisory.
Source
o Cisco would like the following people for reporting these vulnerabilities:
CVE-2021-1426: Can Huang and Xinhui Han at Wangxuan Institute of
Computer Technology, Peking University, and Lasse Trolle Borup of
Danish Cyber Defence
CVE-2021-1427: Lockheed Martin Red Team and Antoine Goichot of PwC
Luxembourg's Cybersecurity team
CVE-2021-1428, CVE-2021-1429, CVE-2021-1430, and CVE-2021-1496:
Lockheed Martin Red Team
Cisco Security Vulnerability Policy
o To learn about Cisco security vulnerability disclosure policies and
publications, see the Security Vulnerability Policy . This document also
contains instructions for obtaining fixed software and receiving security
vulnerability information from Cisco.
URL
o https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-anyconnect-code-exec-jR3tWTA6
Revision History
o +----------+---------------------------+----------+--------+--------------+
| Version | Description | Section | Status | Date |
+----------+---------------------------+----------+--------+--------------+
| 1.0 | Initial public release. | - | Final | 2021-MAY-05 |
+----------+---------------------------+----------+--------+--------------+
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