Cisco Meraki MX Firmware: Use of Uninitialized Variable
CVE-2025-20212 is a high-severity use of uninitialized variable vulnerability in Cisco Meraki MX Firmware from Cisco, with a CVSS 3.1 base score of 7.7 out of 10. It can be exploited remotely over the network by an attacker with a low-privileged account, without any action from a user. Affected Cisco Meraki MX Firmware versions: 16.2; 16.3; 16.4, and others listed below. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.71% chance of exploitation within 30 days, higher than 54% of scored CVEs.
High severity with no evidence of exploitation so far.
What to do
- Check which version of Cisco Meraki MX Firmware you run against the affected versions below, and install the vendor's latest release.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Cisco | Cisco Meraki MX Firmware | 16.2; 16.3; 16.4; 16.5; 16.6; 17.3; 17.6; 17.7; and 6 more ranges | Not stated |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- LowA basic user account is enough.
- User interaction
- NoneNo action by a victim is required.
- Scope
- ChangedThe attack can reach beyond the vulnerable component into other systems.
- Confidentiality
- NoneNo data is disclosed.
- Integrity
- NoneNothing can be modified.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H. Scored by CNA (cisco.com).
Official description
A vulnerability in the Cisco AnyConnect VPN server of Cisco Meraki MX and Cisco Meraki Z Series devices could allow an authenticated, remote attacker to cause a denial of service (DoS) condition in the Cisco AnyConnect service on an affected device. To exploit this vulnerability, the attacker must have valid VPN user credentials on the affected device. This vulnerability exists because a variable is not initialized when an SSL VPN session is established. An attacker could exploit this vulnerability by supplying crafted attributes while establishing an SSL VPN session with 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 sessions 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 without manual intervention.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Use of Uninitialized Variable
The code uses a variable that has not been initialized, leading to unpredictable or unintended results.
How developers prevent this class of flaw
- Ensure that critical variables are initialized before first use.
- Most compilers will complain about the use of uninitialized variables if warnings are turned on.
- When using a language that does not require explicit declaration of variables, run or compile the software in a mode that reports undeclared or unknown variables. This may indicate the presence of a typographic error in the variable's name.
More Use of Uninitialized Variable vulnerabilities (CWE-457)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Other references
Other vulnerabilities in Cisco Meraki MX Firmware
- 8.8 High severity
- 8.8 High severity
- 7.4 High severity
- 8.2 High severity
- 7.5 High severity
- 9.6 Critical severity
Recent Use of Uninitialized Variable vulnerabilities
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
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