CVE-2026-20039
Cisco Adaptive Security Appliance and Firepower Threat Defense Software SSL VPN Authentication Denial of Service Vulnerability
Severity
High 8.6
CVSS 3.1
Exploited
Not listed
EPSS
0.004
28.5th percentile
Discovered by
Vendor
Published by the vendor
Published
Mar 4, 2026
Assigned by cisco
Description
A vulnerability in the VPN web server 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 a denial of service (DoS) condition on an affected device. This vulnerability is due to ineffective memory management of the VPN web server. An attacker could exploit this vulnerability by sending a large number of crafted HTTP requests to an affected device. A successful exploit could allow the attacker to cause the device to reload, resulting in a DoS condition.
Weakness: CWE-244
Affected products
| Vendor | Product | Category | Matched by |
|---|---|---|---|
| Cisco | Cisco Adaptive Security Appliance (ASA) | Firewall / NGFW | cna-assigner |
| Cisco | Cisco Secure Firewall | Firewall / NGFW | cna-assigner |
Vendor-reported affected versions (2)
- Cisco · Cisco Secure Firewall Adaptive Security Appliance (ASA) Software
- Cisco · Cisco Secure Firewall Threat Defense (FTD) Software