Cisco Security Advisory
Cisco AnyConnect Secure Mobility Client for Windows DLL and Executable Hijacking Vulnerabilities
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CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H/E:X/RL:X/RC:X
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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://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-anyconnect-code-exec-jR3tWTA6
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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
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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:HCisco 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:HCisco 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:HCisco 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:HCisco 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
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There are no workarounds that address these vulnerabilities.
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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.htmlAdditionally, 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 Identifiers Affected Releases of Cisco AnyConnect
Secure Mobility Client for WindowsFirst Fixed Release for This Vulnerability 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:
- Click Browse all.
- Choose Security > VPN and Endpoint Security Clients > Cisco VPN Clients > AnyConnect Secure Mobility Client > AnyConnect Secure Mobility Client v4.x.
- Choose a release from the left pane of the AnyConnect Secure Mobility Client v4.x page.
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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.
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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
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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.
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Show LessVersion Description Section Status Date 1.0 Initial public release. - Final 2021-MAY-05
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