CVE-2024-20499Network attack vector

VPN service restart via malformed session parameters

Published Oct 2, 2024 · Updated Jun 4, 2025

Denial of service in Cisco Meraki MX firmware allows remote attackers to restart the AnyConnect VPN server via crafted HTTPS requests. The server insufficiently validates client-supplied parameters while establishing an SSL VPN session, permitting an out-of-bounds write during TLS or DTLS packet processing. AnyConnect must be enabled; exploitation drops established SSL VPN connections, and sustained requests block new connections until traffic stops.

CVSS severity8.6
High
EPSS probability0.51%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in Cisco Meraki MX firmware allows remote attackers to restart the AnyConnect VPN server via crafted HTTPS requests. The server insufficiently validates client-supplied parameters while establishing an SSL VPN session, permitting an out-of-bounds write during TLS or DTLS packet processing. AnyConnect must be enabled; exploitation drops established SSL VPN connections, and sustained requests block new connections until traffic stops.

The record

CVE
CVE-2024-20499
Published
Oct 2, 2024
Updated
Jun 4, 2025
Vendor
ClamAV
Product
Cisco Meraki MX Firmware
Classifications
CWE-787, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 2, 2024CVE publishedPublication date reported by the CVE source.
  2. Jun 4, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0
  2. Affected versionversion=N/A

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

ClamAV · Cisco Meraki MX Firmwareversion=0; version=N/A
ClamAV · Cisco Meraki Z1 Firmwareversion=0

Published CVSS scores

7.5NIST National Vulnerability DatabaseCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
8.6Cisco Systems, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H/E:X/RL:X/RC:X

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-787Out-of-bounds Write
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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