CyberSecBulletin
CVE-2022-20933NVD status: Modified

Cisco Meraki MX Firmware: Failure to Handle Missing Parameter

Published Updated By the CyberSecBulletin desk

CVE-2022-20933 is a high-severity failure to handle missing parameter vulnerability in Cisco Meraki MX Firmware from Cisco, with a CVSS 3.1 base score of 8.6 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. There is no confirmed exploitation so far. EPSS estimates a 1.15% chance of exploitation within 30 days, higher than 67% of scored CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update Meraki Mx64 Firmware to 16.16.6 or 17.10.1, whichever matches your release line, or a later version.
  2. Update Meraki Mx64w Firmware to 16.16.6 or 17.10.1, whichever matches your release line, or a later version.
  3. Update Meraki Mx65 Firmware to 16.16.6 or 17.10.1, whichever matches your release line, or a later version.
  4. Read the advisory on tools.cisco.com for workarounds and exact fixed builds.
  5. Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.

Affected products and versions

VendorProductAffected versionsFixed in
CiscoCisco Meraki MX FirmwareNot specified in the recordNot stated
CiscoMeraki Mx64 Firmware16.2.0 up to, but not including, 16.16.6; 17.0.0 up to, but not including, 17.10.116.16.6, 17.10.1
CiscoMeraki Mx64w Firmware16.2.0 up to, but not including, 16.16.6; 17.0.0 up to, but not including, 17.10.116.16.6, 17.10.1
CiscoMeraki Mx65 Firmware16.2.0 up to, but not including, 16.16.6; 17.0.0 up to, but not including, 17.10.116.16.6, 17.10.1
CiscoMeraki Mx65w Firmware16.2.0 up to, but not including, 16.16.6; 17.0.0 up to, but not including, 17.10.116.16.6, 17.10.1
CiscoMeraki Mx67 Firmware16.2.0 up to, but not including, 16.16.6; 17.0.0 up to, but not including, 17.10.116.16.6, 17.10.1
CiscoMeraki Mx67cw Firmware16.2.0 up to, but not including, 16.16.6; 17.0.0 up to, but not including, 17.10.116.16.6, 17.10.1
CiscoMeraki Mx67w Firmware16.2.0 up to, but not including, 16.16.6; 17.0.0 up to, but not including, 17.10.116.16.6, 17.10.1
CiscoMeraki Mx68 Firmware16.2.0 up to, but not including, 16.16.6; 17.0.0 up to, but not including, 17.10.116.16.6, 17.10.1
CiscoMeraki Mx68cw Firmware16.2.0 up to, but not including, 16.16.6; 17.0.0 up to, but not including, 17.10.116.16.6, 17.10.1
CiscoMeraki Mx68w Firmware16.2.0 up to, but not including, 16.16.6; 17.0.0 up to, but not including, 17.10.116.16.6, 17.10.1
CiscoMeraki Mx75 Firmware16.2.0 up to, but not including, 16.16.6; 17.0.0 up to, but not including, 17.10.116.16.6, 17.10.1
CiscoMeraki Mx84 Firmware16.2.0 up to, but not including, 16.16.6; 17.0.0 up to, but not including, 17.10.116.16.6, 17.10.1
CiscoMeraki Mx85 Firmware16.2.0 up to, but not including, 16.16.6; 17.0.0 up to, but not including, 17.10.116.16.6, 17.10.1
CiscoMeraki Mx95 Firmware16.2.0 up to, but not including, 16.16.6; 17.0.0 up to, but not including, 17.10.116.16.6, 17.10.1
CiscoMeraki Mx100 Firmware16.2.0 up to, but not including, 16.16.6; 17.0.0 up to, but not including, 17.10.116.16.6, 17.10.1
CiscoMeraki Mx105 Firmware16.2.0 up to, but not including, 16.16.6; 17.0.0 up to, but not including, 17.10.116.16.6, 17.10.1
CiscoMeraki Mx250 Firmware16.2.0 up to, but not including, 16.16.6; 17.0.0 up to, but not including, 17.10.116.16.6, 17.10.1
CiscoMeraki Mx400 Firmware16.2.0 up to, but not including, 16.16.6; 17.0.0 up to, but not including, 17.10.116.16.6, 17.10.1
CiscoMeraki Mx450 Firmware16.2.0 up to, but not including, 16.16.6; 17.0.0 up to, but not including, 17.10.116.16.6, 17.10.1
CiscoMeraki Mx600 Firmware16.2.0 up to, but not including, 16.16.6; 17.0.0 up to, but not including, 17.10.116.16.6, 17.10.1
CiscoMeraki Vmx Firmware16.2.0 up to, but not including, 16.16.6; 17.0.0 up to, but not including, 17.10.116.16.6, 17.10.1
CiscoMeraki Z3c FirmwareNot specified in the recordNot stated
CiscoMeraki Z3 FirmwareNot specified in the recordNot 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
NoneNo account or login is needed.
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:N/UI:N/S:C/C:N/I:N/A:H. Scored by NVD.

Scoring systemScoreSeverityScored by
CVSS 3.18.6HighCNA (cisco.com)
CVSS 3.18.6HighNVD

Official description

A vulnerability in the Cisco AnyConnect VPN server of Cisco Meraki MX and Cisco Meraki Z3 Teleworker Gateway devices could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. This vulnerability is due to insufficient validation of client-supplied parameters while establishing an SSL VPN session. An attacker could exploit this vulnerability by crafting a malicious request and sending it to the affected device. A successful exploit could allow the attacker to cause the Cisco AnyConnect VPN server to crash and restart, resulting in the failure of the established SSL VPN connections 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. Note: When the attack traffic stops, the Cisco AnyConnect VPN server recovers gracefully without requiring manual intervention. Cisco Meraki has released software updates that address this vulnerability.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Failure to Handle Missing Parameter

If too few arguments are sent to a function, the function will still pop the expected number of arguments from the stack. Potentially, a variable number of arguments could be exhausted in a function as well.

How developers prevent this class of flaw

  • This issue can be simply combated with the use of proper build process.
  • Forward declare all functions. This is the recommended solution. Properly forward declaration of all used functions will result in a compiler error if too few arguments are sent to a function.

More Failure to Handle Missing Parameter vulnerabilities (CWE-234)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: partial).
  3. Record last changed materially (score, affected products, status or references).

References

Other vulnerabilities in Cisco Meraki MX Firmware

All Cisco Meraki MX Firmware vulnerabilities

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