CVE-2026-76418: Cisco Secure Firewall ASA Software and Cisco Secure FTD Software Unchecked Return Value to NULL Pointer Dereference Vulnerability
Cisco · Secure Firewall ASA Software and Cisco Secure FTD Software · NVD published 2026-10-29 · posted 2026-11-04 · last modified 2026-10-30
CVE-2026-76418 at a glance
CVE-2026-76418 is a high-severity vulnerability in Cisco Secure Firewall ASA Software and Cisco Secure FTD Software, with a CVSS 3.1 base score of 8.6. NVD published it on 2026-10-29 and classifies the weakness as CWE-690. CISA added it to the Known Exploited Vulnerabilities catalog on 2026-10-29; the federal remediation due date is 2026-11-01. FIRST EPSS puts the probability of exploitation activity in the next 30 days at 0.82% (percentile 57.3, scored 2026-11-03). NVD configuration data lists a fixed release for 11 products, for example cisco adaptive security appliance software 9.16.4.104. CVERadar maps 1 MITRE ATT&CK technique across Impact, inferred from the CWE and the description. Its CVERadar threat level is 58/100.
What it is
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.
| Weakness | CWE-690 definition |
|---|---|
| CVSS vector | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H (source: Cisco) |
| CISA due date | 2026-11-01 (for US federal agencies under BOD; a good deadline for everyone) |
| ATT&CK tactics | Impact |
CVERadar report: CVE-2026-76418: Cisco Secure Firewall ASA Software and Cisco Secure FTD Software flaw exploited in the wild
What this means for a small business
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.
Keeping Cisco Secure Firewall ASA Software and Cisco Secure FTD Software patched is easier with someone assigned to it; LayerLogix manages firewalls for businesses that need that help.
Built from the CISA KEV entry and the NVD record for CVE-2026-76418; nothing here goes beyond those sources.
Exploitation evidence
First exploit evidence seen: 2026-10-29 (earliest date across the sources below).
Exploited in the wild
- CISA KEV: listed since 2026-10-29. CISA KEV listing
Sources: CISA KEV.
Defend the Chain
The attack chain for CVE-2026-76418 laid across the MITRE ATT&CK Enterprise tactics. Solid cards come from the MITRE CTID KEV mappings; dashed cards are inferred by CVERadar from the CWE or description. Correct defences are real ATT&CK mitigations for that technique.
Pick a red technique card on the board, then choose the defence that stops it.
Defend against T1499 Endpoint Denial of Service Inferred
Inferred from description keywords
Patches, mitigations and detection
CISA 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. (source: CISA KEV)
Fixed versions
- cisco adaptive security appliance software: upgrade to 9.16.4.104 or later
- cisco adaptive security appliance software: upgrade to 9.18.4.96 or later (affected from 9.18)
- cisco adaptive security appliance software: upgrade to 9.20.4.50 or later (affected from 9.19)
- cisco adaptive security appliance software: upgrade to 9.22.3.200 or later (affected from 9.22)
- cisco adaptive security appliance software: upgrade to 9.23.1.48 or later (affected from 9.23)
- cisco adaptive security appliance software: upgrade to 9.24.1.27 or later (affected from 9.24.1)
- cisco secure firewall threat defense: upgrade to 7.0.11 or later
- cisco secure firewall threat defense: upgrade to 7.2.13 or later (affected from 7.2.0)
- cisco secure firewall threat defense: upgrade to 7.4.9 or later (affected from 7.3.0)
- cisco secure firewall threat defense: upgrade to 7.7.14 or later (affected from 7.7.0)
- cisco secure firewall threat defense: upgrade to 10.0.3 or later (affected from 10.0.0)
Derived from the NVD CPE configuration (versionEndExcluding / versionEndIncluding). Always confirm with the vendor advisory.
Vendor advisories and patches
- Cisco vendor advisory (sec.cloudapps.cisco.com) (CISA KEV notes)
MITRE ATT&CK mitigations for this chain
- M1037 Filter Network Traffic (for T1499) : Leverage services provided by Content Delivery Networks (CDN) or providers specializing in DoS mitigations to filter traffic upstream from services. Filter boundary traffic by blocking source addresses sourcing the attack, blocking ports that are being targeted, or blocking protocols being used for transport. To defend
Detection Generic guidance
- Impact: Monitor service availability, unexpected encryption activity and mass file changes.
Response checklist Generic guidance
- Inventory: find every instance of the affected product and version (include internet-facing and forgotten ones).
- Patch or mitigate per the vendor advisory; if you cannot patch, remove internet exposure or apply the vendor workaround.
- Assume compromise if the system was exposed before patching: hunt for the indicators in the advisory and review logs back to the disclosure date.
- Rotate credentials and secrets stored on or used by the affected system if compromise cannot be ruled out.
Sources
- NVD: CVE-2026-76418
- CVE.org record for CVE-2026-76418
- CISA Known Exploited Vulnerabilities catalog
- FIRST EPSS score for CVE-2026-76418 (2026-11-03)
- CISA government advisory (cisa.gov) cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-76418