dbcve.org
Meraki Z4c FirmwareOperating system · Cisco

CVE-2024-20499

HIGH · 7.5 CVSS v3.1 Published 2024-10-02
Fix available
A fix is available. Upgrade to 18.211.2 or later.
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
Multiple vulnerabilities in the Cisco AnyConnect VPN server of Cisco Meraki MX and Cisco Meraki Z Series Teleworker Gateway devices could allow an unauthenticated, remote attacker to cause a DoS condition in the AnyConnect service on an affected device. These vulnerabilities are due to insufficient validation of client-supplied parameters while establishing an SSL VPN session. An attacker could exploit these vulnerabilities by sending a crafted HTTPS request to the VPN server of an affected device. A successful exploit could allow the attacker to cause the Cisco AnyConnect VPN server to restart, resulting in the failure of the established SSL VPN connections and forcing remote users to initiate a new VPN connection and reauthenticate. A sustained attack could prevent new SSL VPN connections from being established. Note: When the attack traffic stops, the Cisco AnyConnect VPN server recovers gracefully without requiring manual intervention.

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 the Cisco AnyConnect VPN server of Cisco Meraki MX and Z Series Teleworker Gateway devices allow an unauthenticated remote attacker to cause DoS by sending crafted HTTPS requests with insufficiently validated client-supplied parameters during SSL VPN session establishment, causing the VPN server to restart and drop existing connections.

MitigationApply Cisco's vendor patches for Meraki MX and Z Series devices when available; implement network-level rate limiting or access controls to limit exposure to malicious VPN requests until the fix is deployed.

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
Meraki Z4c FirmwareOperating system
Affected:>= 16.2, < 18.211.2
Meraki Z4 FirmwareOperating system
Affected:>= 16.2, < 18.211.2
Meraki Z3c FirmwareOperating system
Affected:>= 16.2, < 18.211.2
Meraki Z3 FirmwareOperating system
Affected:>= 16.2, < 18.211.2
Meraki Vmx FirmwareOperating system
Affected:>= 16.2, < 18.211.2
Meraki Mx600 FirmwareOperating system
Affected:>= 16.2, < 18.211.2
Meraki Mx450 FirmwareOperating system
Affected:>= 16.2, < 18.211.2
Meraki Mx400 FirmwareOperating system
Affected:>= 16.2, < 18.211.2

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
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/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 the Meraki device model
    Check the device dashboard or CLI output for the exact model number (Z4c, Z4, Z3c, Z3, Vmx, Mx600, Mx450, or Mx400)
    Affected if Device is not one of these eight models - the vulnerability only applies to these specific models
  2. Check the installed firmware version
    Access the Meraki dashboard under Network > Appliance > General or use the CLI command 'show version' to retrieve the current firmware release
    Affected if Firmware version is 16.2 or higher but below 18.211.2 - versions outside this range are not affected
  3. Verify SSL VPN is enabled
    Navigate to Security & SD-WAN > Site-to-site VPN or AnyConnect settings in the Meraki dashboard, or check via CLI with 'show vpn'
    Affected if SSL VPN / AnyConnect is actively configured - the vulnerability is only exploitable when the VPN server is enabled and accepting connections

A user is affected if they run any of the eight listed Meraki models with firmware between 16.2 and 18.211.2 and have SSL VPN functionality enabled.

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
Upgrade available Upgrade to 18.211.2 or later
Fixed in 18.211.2
Interim mitigation

Apply Cisco's vendor patches for Meraki MX and Z Series devices when available; implement network-level rate limiting or access controls to limit exposure to malicious VPN requests until the fix is deployed.

Recommended fix High confidence

Firmware version 18.211.2 or later

  1. Log in to the Meraki Dashboard and navigate to the affected device (MX security appliance or Z Series Teleworker Gateway)
  2. Navigate to the device's Firmware upgrade settings or check the current firmware version under the device summary
  3. Confirm the current firmware version is between 16.2 and 18.211.1 (inclusive of 16.2, exclusive of 18.211.2)
  4. Initiate a firmware upgrade to version 18.211.2 or later through the Meraki Dashboard or device management interface
  5. Wait for the firmware upgrade to complete and the device to reboot
  6. Verify the new firmware version is 18.211.2 or higher
  7. Test the Cisco AnyConnect VPN service to confirm it is operational
Caveat Review Meraki release notes for version 18.211.2 to check for any configuration or feature changes that may affect your deployment

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

Fix this in Meraki Z4c Firmware Scoped from the published advisory
  • Consultation1.0 h
  • Implementation2.0 h
  • Testing2.0 h
  • Review / QA1.0 h
6.0 hours of engineering $1,040
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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-2024-20499 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