dbcve.org
Anyconnect Secure Mobility ClientApplication · Cisco

CVE-2023-20240

MEDIUM · 5.5 CVSS v3.1 Published 2023-11-22
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
57/100
Remediation priority · Elevated
Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Multiple vulnerabilities in Cisco Secure Client Software, formerly AnyConnect Secure Mobility Client, could allow an authenticated, local attacker to cause a denial of service (DoS) condition on an affected system. These vulnerabilities are due to an out-of-bounds memory read from Cisco Secure Client Software. An attacker could exploit these vulnerabilities by logging in to an affected device at the same time that another user is accessing Cisco Secure Client on the same system, and then sending crafted packets to a port on that local host. A successful exploit could allow the attacker to crash the VPN Agent service, causing it to be unavailable to all users of the system. To exploit these vulnerabilities, the attacker must have valid credentials on a multi-user system.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Multiple vulnerabilities in Cisco Secure Client (formerly AnyConnect) allow an authenticated local attacker on a multi-user system to cause a denial of service. The vulnerabilities stem from out-of-bounds memory reads in the VPN Agent service. An attacker with valid credentials can exploit this by logging in simultaneously with another user accessing Cisco Secure Client and sending crafted packets to a local host port, causing the VPN Agent service to crash and become unavailable to all users.

MitigationApply the vendor-supplied patches or upgrade to a fixed version of Cisco Secure Client. On multi-user systems, limit concurrent user access and monitor for unusual VPN Agent service behavior.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Anyconnect Secure Mobility ClientApplication
Affected:= 4.9.00086= 4.9.01095= 4.9.02028= 4.9.03047= 4.9.03049= 4.9.04043= 4.9.04053= 4.9.05042= 4.9.06037
Secure ClientApplication
Affected:= 4.10.00093= 4.10.01075= 4.10.02086= 4.10.03104= 4.10.04065= 4.10.04071= 4.10.05085= 4.10.05095= 4.10.05111= 4.10.06079= 4.10.06090= 4.10.07061

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify installed Cisco client software
    Open Programs and Features (Windows) or check /Applications (macOS) for Cisco Secure Client, Cisco AnyConnect Secure Mobility Client, or AnyConnect entries. Use command: 'wmic product get name,version' (Windows) or 'ls /Applications | grep -i anyconnect' (macOS)
    Affected if The installed software name matches Cisco Secure Client or Cisco AnyConnect Secure Mobility Client and version equals any of the listed affected versions (4.9.00086 through 4.9.06037 for AnyConnect, or 4.10.00093 through 4.10.07061 for Secure Client)
  2. Locate the VPN Agent service
    Windows: Open Services console and find 'Cisco Secure Client' or 'Cisco AnyConnect' service, or run 'sc query all | findstr -i cisco'. macOS: Run 'launchctl list | grep -i anyconnect' or check for 'acumn' process
    Affected if The VPN Agent service (commonly named Cisco Secure Client, Cisco AnyConnect VPN Agent, or acumn) exists on the system
  3. Verify VPN Agent service is running
    Windows: Run 'sc query <service_name>' where service name is from step 2. Check for STATE: RUNNING. macOS: Run 'ps aux | grep acumn' to confirm the process is active
    Affected if The VPN Agent service process is currently running - this is required for the vulnerability to be exploitable
  4. Determine if system supports multiple concurrent users
    Windows: Check system type - servers typically allow multiple RDP sessions. Run 'query user' to list active sessions. macOS: Check for Fast User Switching enabled: 'defaults read /Library/Preferences/com.apple.loginwindow.plist MultipleSessionEnabled'
    Affected if The system is configured to allow multiple users to be logged on simultaneously (multi-user system with concurrent sessions)

You are affected if Cisco Secure Client or AnyConnect is installed with a version matching any of the affected versions listed AND the VPN Agent service is running on a multi-user system where concurrent user access is possible.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Apply the vendor-supplied patches or upgrade to a fixed version of Cisco Secure Client. On multi-user systems, limit concurrent user access and monitor for unusual VPN Agent service behavior.

Recommended fix Moderate confidence

Latest Cisco Secure Client release (contact Cisco TAC for specific fixed version for 4.9.x and 4.10.x branches)

  1. Navigate to Cisco Software Downloads (software.cisco.com) and search for Cisco Secure Client or AnyConnect
  2. Locate the Cisco Secure Client software and download the latest stable release version
  3. Uninstall the current version of Cisco Secure Client from the affected system
  4. Install the latest version of Cisco Secure Client on the system
  5. Restart the VPN Agent service or reboot the system to ensure the new version is fully operational
  6. Verify the VPN Agent service is running and accessible to all users
Caveat Review Cisco release notes for any configuration or feature changes between affected and fixed versions before upgrading

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Anyconnect Secure Mobility Client Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing2.0 h
  • Review / QA1.0 h
9.0 hours of engineering $1,600
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2023-20240 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data