CVE-2026-76418: Cisco Secure Firewall ASA Software and Cisco Secure FTD Software flaw exploited in the wild

A vulnerability in the Remote Access SSL VPN service of Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause the device to reload unexpectedly, resulting in a denial of service (DoS) condition. This vulnerability is due to logic errors when secondary authentication is configured on a tunnel group. An attacker could exploit this vulnerability by sending a crafted request when connecting to the SSL remote access VPN. A successful exploit could allow the attacker to cause the affected device to reload, resulting in a DoS condition.

• Severity: HIGH (CVSS 3.1 8.6, vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H).
• Weakness: CWE-690.
• NVD published 2026-10-28, status Analyzed.

Anyone running Cisco Secure Firewall ASA Software and Cisco Secure FTD Software in the version ranges below. Internet-facing instances are the priority.

• cisco adaptive security appliance software: up to (not including) 9.16.4.104.
• cisco adaptive security appliance software: from 9.18 up to (not including) 9.18.4.96.
• cisco adaptive security appliance software: from 9.19 up to (not including) 9.20.4.50.
• cisco adaptive security appliance software: from 9.22 up to (not including) 9.22.3.200.
• cisco adaptive security appliance software: from 9.23 up to (not including) 9.23.1.48.
• cisco adaptive security appliance software: from 9.24.1 up to (not including) 9.24.1.27.
• cisco secure firewall threat defense: up to (not including) 7.0.11.
• cisco secure firewall threat defense: from 7.2.0 up to (not including) 7.2.13.
• cisco secure firewall threat defense: from 7.3.0 up to (not including) 7.4.9.
• cisco secure firewall threat defense: from 7.7.0 up to (not including) 7.7.14.
• cisco secure firewall threat defense: from 7.6.0 up to and including 7.6.7.

Version ranges come from the NVD CPE configuration. Confirm against the vendor advisory before you rely on them.

• Exploited in the wild: added to the CISA Known Exploited Vulnerabilities catalog on 2026-10-29; federal remediation due date 2026-11-01.

CISA added CVE-2026-76418 to its Known Exploited Vulnerabilities catalog on 2026-10-29. A KEV listing means CISA has evidence that attackers are using the flaw against real systems, not just that it could be used.

If your business runs Cisco Secure Firewall ASA Software and Cisco Secure FTD Software, put this at the top of the patch list. CISA gave US federal agencies until 2026-11-01 to deal with it, and that is a sensible deadline for a small business too.

• Patch. Update to a fixed release: cisco adaptive security appliance software 9.16.4.104 or later; cisco adaptive security appliance software 9.18.4.96 or later; cisco adaptive security appliance software 9.20.4.50 or later. These versions come from NVD's configuration data, so confirm them against the advisory from Cisco.
• If you cannot patch yet. Follow CISA's required action: Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.
• Check your exposure. Find out whether Cisco Secure Firewall ASA Software and Cisco Secure FTD Software can be reached from the internet, for example a VPN portal, an admin login page or a file-transfer site. Your firewall's port-forwarding rules and your IT provider's list of public-facing systems are the quickest places to look. Exposed copies come first.
• When to call IT support. Call your IT support provider now if you run Cisco Secure Firewall ASA Software and Cisco Secure FTD Software and cannot confirm it is updated, if it was reachable from the internet before you patched it, or if you notice accounts, sign-ins or files you do not recognise. The last two can mean the system was already hit, and checking that properly takes someone who can read the logs.

• EPSS (probability of exploitation activity in the next 30 days): 0.82%, higher than 57% of all scored CVEs (as of 2026-11-03).
• CVERadar threat level: 58/100 (see methodology).
• Likely ATT&CK techniques: T1499 Endpoint Denial of Service (inferred).

1. Find every instance. List where Cisco Secure Firewall ASA Software and Cisco Secure FTD Software runs, including test, DR and forgotten internet-facing systems, and record the installed version.

   show version

2. Upgrade to a fixed release. cisco adaptive security appliance software: 9.16.4.104 or later; cisco adaptive security appliance software: 9.18.4.96 or later; cisco adaptive security appliance software: 9.20.4.50 or later; cisco adaptive security appliance software: 9.22.3.200 or later. Get the build from the vendor advisory.
3. If you can't patch today, follow CISA's required action: Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.
4. Verify the fix. Re-run the version check above on every instance and confirm it reports the fixed build (9.16.4.104 or later). Re-scan from outside if the service is exposed.
5. Hunt for signs of earlier compromise. If the system was exposed before you patched, assume it may have been hit and check the items below.
6. Rotate credentials stored on or used by the affected system if you cannot rule out compromise, and keep the logs you reviewed.

Detection hints

• T1499 Endpoint Denial of Service: Monitor availability and crash/restart counts of the affected service.

Detection commands are generic starting points, not CVE-specific signatures. Use the indicators from the vendor advisory when it publishes them.

• NVD: CVE-2026-76418 nvd.nist.gov/vuln/detail/CVE-2026-76418
• CVE.org record www.cve.org/CVERecord?id=CVE-2026-76418
• Vendor link from CISA KEV sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/
• CISA KEV catalog www.cisa.gov/known-exploited-vulnerabilities-catalog
• FIRST EPSS (2026-11-03) api.first.org/data/v1/epss?cve=CVE-2026-76418