CVE-2026-20349 Cisco Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD) Heap Inspection
Unauthenticated remote attackers can cause Cisco ASA and FTD devices to reload via crafted HTTP requests to the SSL VPN service, resulting in denial of service.
- Exploited in the wild
- Since 11 Aug 2026
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-20349?
CVE-2026-20349 is a high-severity denial of service vulnerability in Cisco Adaptive Security Appliance Software, published on 11 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Weakness: CWE-244
Which versions are affected by CVE-2026-20349?
It affects 2 products.
Products include Cisco Adaptive Security Appliance Software, Cisco Secure Firewall Threat Defense.
How do I fix CVE-2026-20349?
No fix has been published for CVE-2026-20349 yet. Limit exposure of the affected software until one is available. US federal agencies must fix it by 14 Aug 2026.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-20349 being exploited?
Yes. Attackers have exploited CVE-2026-20349 in the wild since at least 11 Aug 2026.
Public exploit code: 1 proofs of concept on GitHub.
Other vulnerabilities in Cisco Adaptive Security Appliance Software
- CVE-2025-20333 Cisco Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD) Buffer Overflow
- CVE-2016-6366 Cisco Adaptive Security Appliance (ASA) SNMP Buffer Overflow
- CVE-2024-20353 Cisco ASA and FTD Denial of Service
- CVE-2016-6367 Cisco Adaptive Security Appliance (ASA) CLI Remote Code Execution
- CVE-2020-3452 Cisco ASA and FTD Read-Only Path Traversal
All Cisco Adaptive Security Appliance Software vulnerabilities
Sources
Also known as GHSA-8x4j-5v9x-9frv.