Report · SecurityWeekAbout CVE-2026-76418Published 29 Oct 2026

Attackers Exploit Second Cisco Firewall VPN Zero-Day Since August

Source SecurityWeek

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Authoritative record:CVE-2026-76418· High 8.6

Not known to be exploited · CVSS 8.6 High.

Data as of 29 Oct 2026, 13:02 UTC

CVSS 3.1 base score

8.6High

How severe the flaw is on the 0–10 CVSS scale.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Changed
Confidentiality: None
Integrity: None
Availability: High

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Changed: An exploited vulnerability can affect resources beyond the security scope managed by the security authority of the vulnerable component. In this case, the vulnerable component and the impacted component are different and managed by different security authorities.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 28 Oct 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
CiscoCisco Secure Firewall Adaptive Security Appliance (ASA) Software	Affected 9.16.1 – 9.24.10 142 affected builds	Fixed in–
CiscoCisco Secure Firewall Threat Defense (FTD) Software	Affected 7.0.0 – 10.1.0 67 affected builds	Fixed in–

AI-suggested

Cisco has released official patches to fix this vulnerability and strongly recommends upgrading to a fixed release. No workarounds fully mitigate the issue; however, customers can reduce exposure by disabling secondary authentication or tunnel group lists, though this reduces VPN security. Organizations should prioritize applying the vendor-provided patches to fully remediate the vulnerability.

Description

CVE-2026-76418 is a high-severity vulnerability in Cisco Secure Firewall ASA and FTD software affecting the Remote Access SSL VPN service. It allows unauthenticated remote attackers to cause the firewall device to restart unexpectedly, disrupting availability. The flaw stems from logic errors in tunnel groups configured with secondary authentication. Cisco has released patches to fix this issue and recommends upgrading. No workarounds exist, though disabling secondary authentication or tunnel group lists can reduce exposure but weaken security. This is the second zero-day exploited in Cisco ASA and FTD VPN services in recent months.

Impact

The vulnerability allows unauthenticated remote attackers to cause Cisco Secure Firewall ASA and FTD devices to restart unexpectedly, disrupting the availability of the firewall and potentially impacting network security and operations. This denial of service can be triggered remotely via the Remote Access SSL VPN service without requiring authentication. The flaw affects devices with secondary authentication enabled in tunnel groups. The impact is high due to the ability to disrupt critical firewall services remotely.

References

securityweek.com/attackers-exploit-second-cisco-firewall-vpn-zero-day-since-august/ (opens in a new tab)

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