Vendor-confirmed zero-dayZero-dayCisco Secure Firewall ASA and Secure FTDFirewalls, VPNs & network gear

Cisco Secure Firewall ASA and Secure FTD: Cisco Secure Firewall Adaptive Security Appliance and Secure Firewall Threat Defense Software Remote Access SSL VPN Tunnel Denial of Service Vulnerability

Who's affected: Anyone using Cisco Secure Firewall ASA and Secure FTD.
Under attack?: Yes. Cisco says: “In October 2026, the Cisco PSIRT became aware of active exploitation of this vulnerability.”
What to do: Install the vendor's latest security update.
Fixed in: See the vendor's advisory
Zero-day?: Yes. The vendor said it was already being exploited when it released the fix, so attackers had it before anyone could patch.

CVE-2026-76418Confirmed by the vendor Oct 28, 2026Source: Cisco advisory ↗

Cisco scorecard: every exploited Cisco flaw →

Client notice ready to send

Fill in the bracketed parts, then paste into an email to your clients or team.

Subject: Security update: Cisco Secure Firewall ASA and Secure FTD

Hi [Client name],

Attackers are actively exploiting a security flaw in Cisco Secure Firewall ASA and Secure FTD.

Who's affected: Anyone using Cisco Secure Firewall ASA and Secure FTD.

What we're doing: [We're checking your systems now and will have the fix in place by DATE.]

What to do: Install the vendor's latest security update.

Fixed in: See the vendor's advisory
Reference: CVE-2026-76418 – https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-tunnel-dos-s6mgkb75

We'll confirm once everything is updated. Reply here with any questions.

[Your name]

Cisco Secure Firewall ASA and Secure FTD: Cisco Secure Firewall Adaptive Security Appliance and Secure Firewall Threat Defense Software Remote Access SSL VPN Tunnel Denial of Service Vulnerability

Also under attack in Firewalls, VPNs & network gear