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Vpn ClientApplication · Cisco

CVE-2002-1106

HIGH · 7.5 CVSS v2.0 Published 2002-10-04
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges 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
Cisco Virtual Private Network (VPN) Client software 2.x.x, and 3.x before 3.5.1C, does not properly verify that certificate DN fields match those of the certificate from the VPN Concentrator, which allows remote attackers to conduct man-in-the-middle attacks.

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 · moderate confidence

Cisco VPN Client 2.x and versions 3.x before 3.5.1C fails to properly validate that Distinguished Name (DN) fields in certificates presented by the VPN Concentrator match expected values. This allows a remote attacker to intercept VPN connections via a man-in-the-middle attack by presenting a fraudulent certificate that the client incorrectly accepts.

MitigationUpgrade to Cisco VPN Client 3.5.1C or later which implements proper certificate DN field validation. Alternatively, deploy certificate pinning or additional PKI controls to ensure only legitimate concentrator certificates are accepted.

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
Vpn ClientApplication
Affected:= 2.0= 3.0= 3.1= 3.5.1

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
Network
Complexity
Low
Authentication
None
Confidentiality
Partial
Integrity
Partial
Availability
Partial

AV:N/AC:L/Au:N/C:P/I:P/A:P

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 Cisco VPN Client version
    On Windows, open Add/Remove Programs or check the program's About/Help section. On Unix, check /opt/cisco-vpn or the package manager. Alternatively, right-click the VPN Client icon and select About or use 'vpnclient version' from command line if available.
    Affected if The installed version is 2.0, 3.0, 3.1, or 3.5.1 (any 2.x or 3.x version before 3.5.1C)
  2. Confirm the client is in active use
    Check if the Cisco VPN Client process is running or if VPN profiles (.pcf files) exist on the system. Look for VPN client software installed and configured for connections.
    Affected if The VPN Client software is installed and configured for use, as the vulnerability affects any connection attempt using the affected client versions
  3. Check certificate verification configuration
    Review the VPN connection profile settings for certificate authentication. Look for options related to certificate validation, CA certificate acceptance, or peer certificate verification in the client configuration.
    Affected if Certificate-based authentication is enabled in the VPN profile, which triggers the flawed DN field validation routine
  4. Verify if connections go to enterprise VPN concentrators
    Examine configured VPN connection profiles to identify target concentrator addresses. Determine if the client is configured to connect to corporate or organizational VPN concentrators that rely on certificate-based authentication.
    Affected if The client is configured to connect to VPN concentrators using the vulnerable certificate validation method

A user is affected if Cisco VPN Client version 2.x or 3.x (before 3.5.1C) is installed and configured for certificate-based VPN connections.

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

Upgrade to Cisco VPN Client 3.5.1C or later which implements proper certificate DN field validation. Alternatively, deploy certificate pinning or additional PKI controls to ensure only legitimate concentrator certificates are accepted.

Fix this in Vpn Client Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA2.0 h
20.0 hours of engineering $3,500
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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-2002-1106 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