CVE-2026-76418highunder attackCWE-690

CVE-2026-76418: high-severity vulnerability in Cisco Secure Firewall Adaptive Security…

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

Published · Updated

51Vexday Risk Score

Prioritize patching. It under exploitation confirmed by CISA and has an official Brazilian government alert.

ssvc Actcvss 8.6epss 0.6%
from disclosure to weapon
Published on NVDOct 28
CISA KEV+1d
exploitation probability
0.6%top 53% of all CVEs
observed exploitation
yesCISA + VulnCheck
Official alert in Brazil

Brazil's federal government published an alert, recommendation or bulletin that cites this vulnerability.

  • CTIR Gov · ALERTA 104/2026 · 29 Oct 2026Vulnerabilidade crítica em produtos Cisco Secure Firewall ASA e Cisco Secure Firewall Threat Defense (FTD)read on gov.br ↗
Source: CTIR Gov (GSI) and CISC Gov.br, under the CC BY-ND 3.0 license.
Action required by CISAfederal deadline: 2026-11-01

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.

In short

A flaw in the remote access SSL VPN of Cisco firewalls can let an unauthenticated attacker crash the device, causing a denial of service for users who depend on it.

Technical detail

An unauthenticated remote attacker can send a crafted request during SSL remote access VPN connection setup to trigger an unexpected reload of Cisco ASA or FTD devices (CWE-690, CVSS 8.6). The precondition is that secondary authentication is configured on a tunnel group, and the logic error results in denial of service without requiring credentials.

Summary generated and translated by AI from the official description.
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.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
Affected products
Cisco · Cisco Secure Firewall Adaptive Security Appliance (ASA) SoftwareCisco · Cisco Secure Firewall Threat Defense (FTD) Software
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References
https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-tunnel-dos-s6mgkb75https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-76418