CVE-2024-20500

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.6% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2024-10-02 · updated 2026-06-17
Weakness: CWE-400

Description

A vulnerability 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. This vulnerability is due to insufficient resource management when establishing TLS/SSL sessions. An attacker could exploit this vulnerability by sending a series of crafted TLS/SSL messages to the VPN server of an affected device. A successful exploit could allow the attacker to cause the Cisco AnyConnect VPN server to stop accepting new connections, preventing new SSL VPN connections from being established. Existing SSL VPN sessions are not impacted. Note: When the attack traffic stops, the Cisco AnyConnect VPN server recovers gracefully without requiring manual intervention.

Affected products

Cisco Meraki Mx100 Firmware: from 16.2 before 18.211.2 — fixed in 18.211.2
Cisco Meraki Mx105 Firmware: from 16.2 before 18.211.2 — fixed in 18.211.2
Cisco Meraki Mx250 Firmware: from 16.2 before 18.211.2 — fixed in 18.211.2
Cisco Meraki Mx400 Firmware: from 16.2 before 18.211.2 — fixed in 18.211.2
Cisco Meraki Mx450 Firmware: from 16.2 before 18.211.2 — fixed in 18.211.2
Cisco Meraki Mx600 Firmware: from 16.2 before 18.211.2 — fixed in 18.211.2
Cisco Meraki Mx64 Firmware: from 17.6.0 through 18.211.2
Cisco Meraki Mx64W Firmware: from 16.2 before 18.211.2 — fixed in 18.211.2
Cisco Meraki Mx65 Firmware: from 17.6.0 before 18.211.2 — fixed in 18.211.2
Cisco Meraki Mx65W Firmware: from 16.2 before 18.211.2 — fixed in 18.211.2
Cisco Meraki Mx67 Firmware: from 16.2 before 18.211.2 — fixed in 18.211.2
Cisco Meraki Mx67C Firmware: from 16.2 before 18.211.2 — fixed in 18.211.2
Cisco Meraki Mx67W Firmware: from 16.2 before 18.211.2 — fixed in 18.211.2
Cisco Meraki Mx68 Firmware: from 16.2 before 18.211.2 — fixed in 18.211.2
Cisco Meraki Mx68Cw Firmware: from 16.2 before 18.211.2 — fixed in 18.211.2
Cisco Meraki Mx68W Firmware: from 16.2 before 18.211.2 — fixed in 18.211.2
Cisco Meraki Mx75 Firmware: from 16.2 before 18.211.2 — fixed in 18.211.2
Cisco Meraki Mx84 Firmware: from 16.2 before 18.211.2 — fixed in 18.211.2
Cisco Meraki Mx85 Firmware: from 16.2 before 18.211.2 — fixed in 18.211.2
Cisco Meraki Mx95 Firmware: from 16.2 before 18.211.2 — fixed in 18.211.2
Cisco Meraki Vmx Firmware: from 16.2 before 18.211.2 — fixed in 18.211.2
Cisco Meraki Z3 Firmware: from 16.2 before 18.211.2 — fixed in 18.211.2
Cisco Meraki Z3C Firmware: from 16.2 before 18.211.2 — fixed in 18.211.2
Cisco Meraki Z4 Firmware: from 16.2 before 18.211.2 — fixed in 18.211.2
Cisco Meraki Z4C Firmware: from 16.2 before 18.211.2 — fixed in 18.211.2

How to fix

Upgrade to a fixed version: Cisco Meraki Mx100 Firmware 18.211.2; Cisco Meraki Mx105 Firmware 18.211.2; Cisco Meraki Mx250 Firmware 18.211.2; Cisco Meraki Mx400 Firmware 18.211.2; Cisco Meraki Mx450 Firmware 18.211.2; Cisco Meraki Mx600 Firmware 18.211.2; Cisco Meraki Mx64W Firmware 18.211.2; Cisco Meraki Mx65 Firmware 18.211.2; Cisco Meraki Mx65W Firmware 18.211.2; Cisco Meraki Mx67 Firmware 18.211.2; Cisco Meraki Mx67C Firmware 18.211.2; Cisco Meraki Mx67W Firmware 18.211.2. Check the vendor advisory for mitigations.

References

https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-meraki-mx-vpn-dos-QTRHzG2

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