CVE-2026-20349 Exploited in the wild
Cisco Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD) Heap Inspection Vulnerability
- Risk score
- 92/100
- CVSS
- 8.6 v3.1
- Published
- 11 Aug 2026
- Added to CISA's exploited list
- 11 Aug 2026
Open in the live forecast Today's forecast
What to know
- What it is
- A vulnerability in the Remote Access SSL VPN service for 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.…
- Affected
- Cisco Secure Firewall Adaptive Security Appliance (asa) And Secure Firewall Threat Defense (ftd)
- Fix
- Apply the vendor's security update; see the linked advisory.
- Exploitation
- Exploited in the wild
Story map
At a glance
Cisco Secure Firewall Adaptive Security Appliance (asa) And Secure Firewall Threat Defense (ftd): Red, act today. A vulnerability in the Remote Access SSL VPN service for 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.…
The flaws
- CVE-2026-20349: Cisco Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD) Heap Inspection Vulnerability (CVSS 8.6 · exploited)
The fix
Fix: Apply the vendor's security update; see the linked advisory.
Who is exposed: Cisco Secure Firewall Adaptive Security Appliance (asa) And Secure Firewall Threat Defense (ftd)
Where it stands
- Exploited in the wild
- On CISA's exploited list since 11 Aug
- US federal deadline 14 Aug
- 2 outlets covering it
How it unfolded
- 11 Aug, CISA (official): Added to the Known Exploited Vulnerabilities list
- 14 Aug, Deadline (official): US federal agencies must have patched
- 29 Oct, SecurityWeek (press): Attackers Exploit Second Cisco Firewall VPN Zero-Day Since August
- 29 Oct, BleepingComputer (press): New Cisco firewall zero-day exploited to crash SSL VPN devices
Connects to
- Reported alongside: Cisco Secure Firewall ASA Software and Cisco Secure FTD Software Unchecked Return Value to NULL Pointer Dereference Vulnerability. CVE-2026-76418 · in 2 of the same articles
- Reported alongside: Cisco Secure Email Gateway Relative Path Traversal Vulnerability. CVE-2026-76519 · in 1 of the same article
In the news
Why it is Red
- CVSS 8.6 high
- Exploited in the wild (CISA KEV)
- Remotely exploitable without logging in
- On your watchlist: cisco
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.
References
Original description
A vulnerability in the Remote Access SSL VPN service for 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 insufficient error checking when processing HTTP requests. An attacker could exploit this vulnerability by sending a crafted HTTP request to the Remote Access SSL VPN service on an affected device. A successful exploit could allow the attacker to cause the affected device to reload, resulting in a DoS condition.
Last activity 11 Aug 2026. Patch Forecast updates every hour.