CVE-2024-20499VulnerabilityPublished 2 Oct 2024Updated 4 Jun 2025

CVE-2024-20499: Cisco Meraki MX Firmware · Out-of-bounds Write

Affects Cisco Meraki MX FirmwareSource CVE Database V5

Not known to be exploited · CVSS 8.6 High.

Data as of 25 Oct 2026, 19:02 UTC

CVSS 3.1 base score

8.6High

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.5% chance of exploitation in 30 days – higher than 42% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Changed
Confidentiality: None
Integrity: None
Availability: High

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Changed: An exploited vulnerability can affect resources beyond the security scope managed by the security authority of the vulnerable component. In this case, the vulnerable component and the impacted component are different and managed by different security authorities.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 2 Oct 2024
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 2026-10-25.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

AI-suggested

To mitigate this vulnerability, European organizations should prioritize the following actions: 1) Apply Cisco's security patches or firmware updates for Meraki MX and Z Series devices as soon as they become available to address the out-of-bounds write flaw. 2) Implement network-level protections such as web application firewalls (WAFs) or intrusion prevention systems (IPS) to detect and block malformed HTTPS requests targeting the VPN server. 3) Restrict VPN server access to trusted IP ranges where possible, limiting exposure to the public internet. 4) Monitor VPN server logs and network traffic for unusual patterns indicative of DoS attempts or malformed requests. 5) Establish redundancy and failover mechanisms for VPN gateways to maintain remote access availability during an attack. 6) Educate IT and security teams on the vulnerability details and incident response procedures to quickly identify and mitigate exploitation attempts. 7) Consider deploying rate limiting or connection throttling on VPN endpoints to reduce the impact of sustained attack traffic. These measures, combined with timely patching, will reduce the risk of successful exploitation and minimize operational disruption.

Description

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.

Impact

For European organizations, this vulnerability poses a significant risk to the availability of secure remote access infrastructure. Many enterprises, government agencies, and critical infrastructure operators in Europe rely on Cisco Meraki MX and Z Series devices to enable remote work and secure VPN connectivity. Exploitation could disrupt remote employee access, delay business operations, and impact productivity. In sectors such as finance, healthcare, and public administration, where secure and reliable VPN connections are essential, this DoS vulnerability could lead to operational downtime and potential regulatory compliance issues related to service availability. Additionally, repeated disruptions could erode user trust in remote access solutions and increase support costs. While the vulnerability does not directly compromise confidentiality or integrity, the denial of service on VPN gateways could indirectly affect incident response and security monitoring capabilities by limiting secure access to internal resources. Given the ongoing geopolitical tensions and increased cyber threat activity targeting European entities, maintaining resilient VPN infrastructure is critical.

References

sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-meraki-mx-vpn-dos-QTRHzG2 (opens in a new tab)

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Exploitation evidence

What to do

Description

AI analysisMachine-generated, updated 6 Jul 2025, 21:39 UTC

Technical details

References

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