CVE-2025-20212
📋 TL;DR
An authenticated attacker with VPN credentials can cause a denial of service on Cisco Meraki MX/Z Series devices by exploiting an uninitialized variable in the AnyConnect VPN server. This forces VPN service restarts, disrupting existing connections and potentially preventing new ones. Organizations using affected Meraki devices with AnyConnect VPN are vulnerable.
💻 Affected Systems
- Cisco Meraki MX Series
- Cisco Meraki Z Series
⚠️ Manual Verification Required
This CVE does not have specific version information in our database, so automatic vulnerability detection cannot determine if your system is affected.
Why? The CVE database entry doesn't specify which versions are vulnerable (no version ranges provided by the vendor/NVD).
🔒 Custom verification scripts are available for registered users. Sign up free to download automated test scripts.
- Review the CVE details at NVD
- Check vendor security advisories for your specific version
- Test if the vulnerability is exploitable in your environment
- Consider updating to the latest version as a precaution
⚠️ Risk & Real-World Impact
Worst Case
Sustained attacks could completely prevent VPN access for remote users, disrupting business operations that rely on remote connectivity.
Likely Case
Intermittent VPN service disruptions requiring users to reconnect, causing productivity loss and connection instability.
If Mitigated
Brief service interruptions during attack periods with automatic recovery once attacks stop.
🎯 Exploit Status
Exploitation requires valid VPN credentials and ability to establish SSL VPN sessions with crafted attributes.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check Cisco advisory for specific fixed firmware versions
Vendor Advisory: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-meraki-mx-vpn-dos-vNRpDvfb
Restart Required: Yes
Instructions:
1. Log into Meraki dashboard 2. Navigate to Security & SD-WAN > Configure > VPN settings 3. Check for firmware updates 4. Apply latest firmware update 5. Reboot affected devices
🔧 Temporary Workarounds
Restrict VPN Access
allLimit VPN access to only necessary users and implement strong authentication controls
Monitor VPN Connections
allImplement monitoring for abnormal VPN connection patterns or repeated authentication attempts
🧯 If You Can't Patch
- Implement network segmentation to isolate VPN traffic and limit blast radius
- Enforce strong VPN credential policies and monitor for credential compromise
🔍 How to Verify
Check if Vulnerable:
Check Meraki dashboard for device firmware version and compare against Cisco advisoryCheck Version:
Check via Meraki dashboard: Organization > Monitor > Devices > select device > Firmware versionVerify Fix Applied:
Verify firmware version has been updated to patched version in Meraki dashboard📡 Detection & Monitoring
Log Indicators:
- Multiple VPN service restarts
- Abnormal VPN session termination patterns
- Repeated authentication from single source
Network Indicators:
- Spike in VPN connection attempts
- Unusual VPN traffic patterns
SIEM Query:
source="meraki" AND (event_type="vpn_restart" OR vpn_status="failed")