CyberSecBulletin
CVE-2024-20499NVD status: Modified

Cisco Meraki MX Firmware: Out-of-bounds Write

Published Updated By the CyberSecBulletin desk

CVE-2024-20499 is a high-severity out-of-bounds write vulnerability in Cisco Meraki MX Firmware from Cisco, with a CVSS 3.1 base score of 7.5 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 0.51% chance of exploitation within 30 days, which is low compared with other CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update Meraki Z4c Firmware to 18.211.2 or a later version.
  2. Update Meraki Z4 Firmware to 18.211.2 or a later version.
  3. Update Meraki Z3c Firmware to 18.211.2 or a later version.
  4. Read the advisory on sec.cloudapps.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_mx0Not stated
Ciscomeraki_z10Not stated
CiscoMeraki Z4c Firmware16.2 up to, but not including, 18.211.218.211.2
CiscoMeraki Z4 Firmware16.2 up to, but not including, 18.211.218.211.2
CiscoMeraki Z3c Firmware16.2 up to, but not including, 18.211.218.211.2
CiscoMeraki Z3 Firmware16.2 up to, but not including, 18.211.218.211.2
CiscoMeraki Vmx Firmware16.2 up to, but not including, 18.211.218.211.2
CiscoMeraki Mx600 Firmware16.2 up to, but not including, 18.211.218.211.2
CiscoMeraki Mx450 Firmware16.2 up to, but not including, 18.211.218.211.2
CiscoMeraki Mx400 Firmware16.2 up to, but not including, 18.211.218.211.2
CiscoMeraki Mx250 Firmware16.2 up to, but not including, 18.211.218.211.2
CiscoMeraki Mx105 Firmware16.2 up to, but not including, 18.211.218.211.2
CiscoMeraki Mx100 Firmware16.2 up to, but not including, 18.211.218.211.2
CiscoMeraki Mx95 Firmware16.2 up to, but not including, 18.211.218.211.2
CiscoMeraki Mx85 Firmware16.2 up to, but not including, 18.211.218.211.2
CiscoMeraki Mx84 Firmware16.2 up to, but not including, 18.211.218.211.2
CiscoMeraki Mx75 Firmware16.2 up to, but not including, 18.211.218.211.2
CiscoMeraki Mx68w Firmware16.2 up to, but not including, 18.211.218.211.2
CiscoMeraki Mx68cw Firmware16.2 up to, but not including, 18.211.218.211.2
CiscoMeraki Mx68 Firmware16.2 up to, but not including, 18.211.218.211.2
CiscoMeraki Mx67w Firmware16.2 up to, but not including, 18.211.218.211.2
CiscoMeraki Mx67c Firmware16.2 up to, but not including, 18.211.218.211.2
CiscoMeraki Mx67 Firmware16.2 up to, but not including, 18.211.218.211.2
CiscoMeraki Mx65w Firmware16.2 up to, but not including, 18.211.218.211.2

Version data comes from the organisation that assigned the CVE; 3 further products are omitted here. 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
UnchangedImpact stays within the vulnerable component.
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:U/C:N/I:N/A:H. Scored by NVD.

Scoring systemScoreSeverityScored by
CVSS 3.18.6HighCNA (cisco.com)
CVSS 3.17.5HighNVD

Official 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.

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

The underlying weakness: Out-of-bounds Write

The product writes data past the end, or before the beginning, of the intended buffer.

How developers prevent this class of flaw

  • Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. For example, many languages that perform their own memory management, such as Java and Perl, are not subject to buffer overflows. Other languages, such as Ada and C#, typically provide overflow protection, but the protection can be disabled by the programmer. Be wary that a language's interface to native code may still be subject to overflows, even if the language itself is theoretically safe.
  • Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. Examples include the Safe C String Library (SafeStr) by Messier and Viega, and the Strsafe.h library from Microsoft. These libraries provide safer versions of overflow-prone string-handling functions.
  • Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index checking. D3-SFCV (Stack Frame Canary Validation) from D3FEND discusses canary-based detection in detail.

More Out-of-bounds Write vulnerabilities (CWE-787)

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

Recent Out-of-bounds Write vulnerabilities

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