Cisco Warns of Actively Exploited ASA and FTD Firewall Zero-Day Crashing SSL VPN Devices
Cisco confirmed active exploitation of CVE-2026-76418, a high-severity denial-of-service zero-day in Adaptive Security Appliance and Firepower Threat Defense software. Unauthenticated attackers can fo
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Cisco has warned customers about an actively exploited zero-day affecting Adaptive Security Appliance (ASA) and Firepower Threat Defense (FTD) software, with the flaw capable of crashing devices that expose SSL VPN access. The issue, tracked as CVE-2026-76418, is a high-severity denial-of-service vulnerability, and Cisco has confirmed active exploitation in the wild, according to BleepingComputer’s report published 2026-10-29. Cisco said patching is required because there is no complete workaround. BleepingComputer, 2026-10-29
What Cisco says is happening
The reported flaw affects ASA and FTD software when SSL VPN is enabled on at least one interface. BleepingComputer reported that the vulnerability stems from logic errors when secondary authentication is configured on a tunnel group using the webvpn keyword. In that configuration, an unauthenticated remote attacker can send a crafted request while connecting to an SSL remote-access VPN and force the affected firewall or VPN device to reload unexpectedly. Cisco PSIRT confirmed active exploitation, but had not disclosed attackers, targeted organizations, or indicators of compromise as of the report date. BleepingComputer, 2026-10-29
What administrators can do
Cisco reportedly said there is no complete workaround, leaving upgrading to a fixed release as the recommended path. For administrators who cannot patch immediately, BleepingComputer reported a temporary measure: disable secondary authentication on DefaultWEBVPNGroup and other configured tunnel groups. That is presented as a stopgap, not a full fix. BleepingComputer, 2026-10-29
Exposure and risk
BleepingComputer cited Shadowserver data showing more than 51,000 internet-exposed Cisco ASA SSL VPN devices. That figure does not prove those systems are vulnerable to exploitation, but it does suggest a large potential attack surface for a flaw tied to SSL VPN access. BleepingComputer, 2026-10-29
Bottom line
The key facts are straightforward: Cisco says CVE-2026-76418 is being actively exploited, the bug can crash affected ASA and FTD devices through crafted SSL VPN requests, and patching is the only complete remedy currently identified. Until fixed releases are in place, organizations running exposed Cisco VPN services should treat this as an immediate operational risk. BleepingComputer, 2026-10-29
Sources and dates
Research completed: 2026-10-30T05:08:17Z
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