dbcve.org
Anyconnect Secure Mobility ClientApplication · Cisco

CVE-2020-3556

HIGH · 7.3 CVSS v3.1 Published 2020-11-06
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
73/100
Remediation priority · Elevated

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
A vulnerability in the interprocess communication (IPC) channel of Cisco AnyConnect Secure Mobility Client Software could allow an authenticated, local attacker to cause a targeted AnyConnect user to execute a malicious script. The vulnerability is due to a lack of authentication to the IPC listener. An attacker could exploit this vulnerability by sending crafted IPC messages to the AnyConnect client IPC listener. A successful exploit could allow an attacker to cause the targeted AnyConnect user to execute a script. This script would execute with the privileges of the targeted AnyConnect user. In order to successfully exploit this vulnerability, there must be an ongoing AnyConnect session by the targeted user at the time of the attack. To exploit this vulnerability, the attacker would also need valid user credentials on the system upon which the AnyConnect client is being run. Cisco has not released software updates that address this vulnerability.

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

A vulnerability in Cisco AnyConnect's interprocess communication (IPC) channel lacks authentication on the IPC listener, allowing an authenticated local attacker to send crafted IPC messages that cause a targeted user with an active AnyConnect session to execute arbitrary scripts with the user's own privileges.

MitigationSince no vendor patch is available, implement compensating controls: restrict local user permissions, monitor for suspicious IPC activity, enforce application whitelisting to block unauthorized script execution, and terminate AnyConnect sessions when not in use.

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\(3052\)= 98.145\(86\)

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
Required
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:H/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. Check if Cisco AnyConnect is installed
    On Windows, check the installed programs list via Control Panel > Programs and Features, or run 'wmic product get name,version' to list installed software. On macOS, check /Applications for AnyConnect or run 'ls /Applications' to see if Cisco AnyConnect Secure Mobility Client.app exists.
    Affected if AnyConnect is not installed means not affected.
  2. Identify the installed AnyConnect version
    On Windows, open Control Panel > Programs and Features, find Cisco AnyConnect Secure Mobility Client and note the version in the 'Version' column. Alternatively, right-click the AnyConnect icon in the system tray, select 'About AnyConnect' to view the full version string including the build number in parentheses.
    Affected if The installed version must match exactly 4.9(3052) or 98.145(86) to be vulnerable.
  3. Check for active AnyConnect sessions
    On Windows, open Task Manager and look for any running 'vpnui.exe' or 'acvpnui.exe' processes in the Processes tab. Also check the system tray for the AnyConnect icon which indicates an active connection or session.
    Affected if The vulnerability requires a target user with an active AnyConnect session. If no session is active, the attack surface is reduced but the software is still vulnerable.
  4. Verify the IPC listener is present
    Open Command Prompt and run 'netstat -ano | findstr 3052' or 'netstat -an' to look for listening ports associated with AnyConnect IPC. Also check running services for 'Cisco AnyConnect Secure Mobility Service' or similar.
    Affected if The IPC channel listener runs when AnyConnect is active. The lack of authentication on this listener is the core vulnerability.

You are affected if Cisco AnyConnect Secure Mobility Client version 4.9(3052) or 98.145(86) is installed AND there is an active AnyConnect session running, allowing any locally authenticated user to potentially send crafted IPC messages to execute arbitrary scripts with the active user's privileges.

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.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Since no vendor patch is available, implement compensating controls: restrict local user permissions, monitor for suspicious IPC activity, enforce application whitelisting to block unauthorized script execution, and terminate AnyConnect sessions when not in use.

Fix this in Anyconnect Secure Mobility Client Scoped from the published advisory
  • Consultation8.0 h
  • Implementation16.0 h
  • Testing8.0 h
  • Review / QA4.0 h
36.0 hours of engineering $6,400
Get help mitigating

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $10,240.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2020-3556 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

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-2020-3556 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

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