Cisco firewalls can be crashed through their VPN.

A flaw in Cisco ASA and FTD firewalls lets anyone on the internet make the device restart through the VPN service. Update to a fixed release.

High Fix available All countries CVE-2026-76418
The issue

What's happening.

Cisco Secure Firewall ASA and FTD are firewalls that protect many company networks. A logic error in the remote access SSL VPN service, when secondary authentication is set up on a tunnel group, lets an attacker with no login send a crafted request that makes the device reload.

The attack causes an outage. Cisco's advisory describes denial of service, not break-in.

The impact

What it means for you.

If the firewall restarts, staff lose their VPN and often the office loses its internet protection until it comes back. Repeated attacks can keep it down.

The fix

How to fix it.

  1. Update to a fixed release from the table, or the one named in Cisco's advisory.
  2. Ask your IT provider whether you use Cisco ASA or Secure Firewall, and whether remote access VPN is turned on.
  3. Check the firewall's management and VPN pages are not open to the whole internet when they do not need to be.
  4. Keep a recent copy of the firewall configuration so you can restore quickly after a restart.
VersionSafe versionStatus
ASA 9.169.16.4.104 or laterFixed
ASA 9.189.18.4.96 or laterFixed
ASA 9.19 and 9.209.20.4.50 or laterFixed
ASA 9.229.22.3.200 or laterFixed
ASA 9.239.23.1.48 or laterFixed
ASA 9.249.24.1.27 or laterFixed
FTD 7.07.0.11 or laterFixed
FTD 7.27.2.13 or laterFixed
FTD 7.4 and 7.37.4.9 or laterFixed
FTD 7.6A release after 7.6.7 (see Cisco)Check
FTD 7.77.7.14 or laterFixed
FTD 10.010.0.3 or laterFixed