Cisco Meraki MX/Meraki Z AnyConnect VPN Server uninitialized variable

CVSS Meta Temp Score
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CTI Interest Score
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7.9$0-$5k0.00

Summaryinfo

A vulnerability marked as critical has been reported in Cisco Meraki MX and Meraki Z. Impacted is an unknown function of the component AnyConnect VPN Server. This manipulation causes uninitialized variable. The identification of this vulnerability is CVE-2025-20271. It is possible to initiate the attack remotely. There is no exploit available. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability classified as critical was found in Cisco Meraki MX and Meraki Z (the affected version is unknown). Affected by this vulnerability is an unknown code of the component AnyConnect VPN Server. The manipulation with an unknown input leads to a uninitialized variable vulnerability. The CWE definition for the vulnerability is CWE-457. The code uses a variable that has not been initialized, leading to unpredictable or unintended results. As an impact it is known to affect availability. The summary by CVE is:

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 denial of service (DoS) condition in the Cisco AnyConnect service on an affected device. This vulnerability is due to variable initialization errors when an SSL VPN session is established. An attacker could exploit this vulnerability by sending a sequence of crafted HTTPS requests to an affected device. A successful exploit could allow the attacker to cause the Cisco AnyConnect VPN server to restart, resulting in the failure of all established SSL VPN sessions and forcing remote users to initiate a new VPN connection and re-authenticate. A sustained attack could prevent new SSL VPN connections from being established, effectively making the Cisco AnyConnect VPN service unavailable for all legitimate users.

It is possible to read the advisory at sec.cloudapps.cisco.com. This vulnerability is known as CVE-2025-20271 since 10/10/2024. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. The technical details are unknown and an exploit is not publicly available.

The vulnerability scanner Nessus provides a plugin with the ID 241193 (Cisco Meraki 16.2 / 17 / 18.1 < 18.1.07.13 / 18.2 < 18.2.11.6 / 19.1 < 19.1.8 DoS (cisco-sa-meraki-mx-vpn-dos-sM5GCfm7)), which helps to determine the existence of the flaw in a target environment.

Upgrading eliminates this vulnerability.

The vulnerability is also documented in the databases at Tenable (241193) and EUVD (EUVD-2025-18656). Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Productinfo

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License

Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 8.0
VulDB Meta Temp Score: 7.9

VulDB Base Score: 7.5
VulDB Temp Score: 7.2
VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA Base Score: 8.6
CNA Vector (cisco): 🔒

CVSSv2info

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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Uninitialized variable
CWE: CWE-457 / CWE-453
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Nessus ID: 241193
Nessus Name: Cisco Meraki 16.2 / 17 / 18.1 < 18.1.07.13 / 18.2 < 18.2.11.6 / 19.1 < 19.1.8 DoS (cisco-sa-meraki-mx-vpn-dos-sM5GCfm7)

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Timelineinfo

10/10/2024 CVE reserved
06/18/2025 +251 days Advisory disclosed
06/18/2025 +0 days VulDB entry created
07/03/2025 +14 days VulDB entry last update

Sourcesinfo

Vendor: cisco.com

Advisory: cisco-sa-meraki-mx-vpn-dos-sM5GCfm7
Status: Confirmed

CVE: CVE-2025-20271 (🔒)
GCVE (CVE): GCVE-0-2025-20271
GCVE (VulDB): GCVE-100-313219
EUVD: 🔒

Entryinfo

Created: 06/18/2025 23:38
Updated: 07/03/2025 01:25
Changes: 06/18/2025 23:38 (62), 06/19/2025 04:28 (1), 06/24/2025 01:46 (1), 07/03/2025 01:25 (2)
Complete: 🔍
Cache ID: 216::103

Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

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