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             AUSCERT External Security Bulletin Redistribution

   Cisco AnyConnect Secure Mobility Client for Linux and Mac OS with VPN
     Posture (HostScan) Module Shared Library Hijacking Vulnerability
                              7 October 2021


        AusCERT Security Bulletin Summary

Product:           AnyConnect Secure Mobility Client
Publisher:         Cisco Systems
Operating System:  Linux variants
Impact/Access:     Root Compromise -- Existing Account
Resolution:        Patch/Upgrade
CVE Names:         CVE-2021-34788  

Original Bulletin: 

- --------------------------BEGIN INCLUDED TEXT--------------------

Cisco AnyConnect Secure Mobility Client for Linux and Mac OS with VPN Posture
(HostScan) Module Shared Library Hijacking Vulnerability

Priority:        High
Advisory ID:     cisco-sa-anyconnect-lib-hija-cAFB7x4q
First Published: 2021 October 6 16:00 GMT
Version 1.0:     Final
Workarounds:     No workarounds available
Cisco Bug IDs:   CSCvz38781
CVE Names:       CVE-2021-34788
CWEs:            CWE-367


  o A vulnerability in the shared library loading mechanism of Cisco AnyConnect
    Secure Mobility Client for Linux and Mac OS could allow an authenticated,
    local attacker to perform a shared library hijacking attack on an affected
    device if the VPN Posture (HostScan) Module is installed on the AnyConnect

    This vulnerability is due to a race condition in the signature verification
    process for shared library files that are loaded on an affected device. An
    attacker could exploit this vulnerability by sending a series of crafted
    interprocess communication (IPC) messages to the AnyConnect process. A
    successful exploit could allow the attacker to execute arbitrary code on
    the affected device with root privileges. To exploit this vulnerability,
    the attacker must have a valid account on the system.

    Cisco has released software updates that address this vulnerability. There
    are no workarounds that address this vulnerability.

    This advisory is available at the following link:

Affected Products

  o Vulnerable Products

    This vulnerability affects devices that are running a vulnerable release of
    Cisco AnyConnect Secure Mobility Client for Linux and Mac OS if the VPN
    Posture (HostScan) Module is installed.

    Note: The VPN Posture (HostScan) Module should not be confused with the ISE
    Posture (SystemScan) Module. The ISE Posture Module is not affected by this

    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 this vulnerability.

    Cisco has confirmed that this vulnerability does not affect the following
    Cisco products:

       AnyConnect Secure Mobility Client for mobile device operating systems
        such as iOS, Android, and Universal Windows Platform
       AnyConnect Secure Mobility Client for Linux and Mac OS with only the
        ISE Posture (SystemScan) Module installed
       AnyConnect Secure Mobility Client for Windows


  o There are no workarounds that address this vulnerability.

Fixed Software

  o Cisco has released free software updates that address the vulnerability
    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:

    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

    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

    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

    Fixed Releases

    Customers are advised to upgrade to an appropriate fixed software release
    as indicated in the following table(s):

    Cisco AnyConnect Secure Mobility Client for Linux and Mac  First Fixed
    OS Release                                                 Release
    Earlier than 4.10.03104                                    4.10.03104

    To download the software from the Software Center on Cisco.com, do the

     1. Click Browse all .
     2. Choose Security > VPN and Endpoint Security 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.

    The Cisco Product Security Incident Response Team (PSIRT) validates only
    the affected and fixed release information that is documented in this

Exploitation and Public Announcements

  o The Cisco PSIRT is not aware of any public announcements or malicious use
    of the vulnerability that is described in this advisory.


  o This vulnerability was found during internal security testing.

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.


  o https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-anyconnect-lib-hija-cAFB7x4q

Revision History

  o +----------+---------------------------+----------+--------+--------------+
    | Version  |        Description        | Section  | Status |     Date     |
    | 1.0      | Initial public release.   | -        | Final  | 2021-OCT-06  |

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