CVE-2026-20039: Cisco Adaptive Security Appliance and Firepower Threat Defense Software SSL VPN Authentication Denial of Service Vulnerability
Cisco · Cisco Secure Firewall Adaptive Security Appliance (ASA) Software
Affected: Cisco Secure Firewall Adaptive Security Appliance (ASA) Software · Exploitation: unlikely (under 1%)
Not in CyberSIXT coverage yet: no article names this CVE. This page shows the public record.
Higher than 35% of scored CVEs
DescriptionCVE.org
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.
Affected products2
From the CVE record. A product or version that is not listed is unknown, not unaffected.
- Cisco · Cisco Secure Firewall Adaptive Security Appliance (ASA) Software9.12.3; 9.12.1; 9.12.2; 9.12.4; 9.12.3.2; 9.12.3.7 and 136 more
- Cisco · Cisco Secure Firewall Threat Defense (FTD) Software6.4.0.1; 6.4.0.2; 6.4.0.5; 6.4.0; 6.4.0.3; 6.4.0.4 and 62 more
On the Atlas
Every published CVE is on the CyberSIXT Atlas, grouped by weakness, vendor and month.
- Exploitation
- Unlikely (under 1%). EPSS under 1%, or no score yet.
- CISA KEV
- Not listed
- Public check
- No public nuclei template
- Vendor
- Cisco
- Published
- March 2026
CoverageNo articles yet
No CyberSIXT article names CVE-2026-20039 yet, so there is no coverage timeline, action brief or change log for it. Everything on this page comes from the public CVE record, CISA KEV, EPSS and the nuclei template index. Search the archive or see the CVEs in the news.