What is CVE-2026-20039?

CVE-2026-20039 is a high-severity vulnerability in Cisco Adaptive_security_appliance_software, classified under CWE-244. CVSS score: 8.6/10. Published 2026-03-04.

How severe is CVE-2026-20039?

High severity. CVSS v3 base score is 8.6 out of 10.

Vulnerability in Cisco Adaptive_security_appliance_software

CVE-2026-20039

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…

EPSS: 0.004 (28.2th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 8.6 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H.

Affected products

Cisco Adaptive_security_appliance_software
Cisco Secure Firewall Adaptive Security Appliance (Asa) Software — versions 9.12.3, 9.12.1, 9.12.2
Cisco Secure Firewall Threat Defense (Ftd) Software — versions 6.4.0.1, 6.4.0.2, 6.4.0.5
Cisco Firepower_threat_defense_software

Weakness classification (CWE)

CWE-244

References

psirt@cisco.com (Vendor Advisory)

Frequently asked questions

What is CVE-2026-20039?: CVE-2026-20039 is a high-severity vulnerability in Cisco Adaptive_security_appliance_software, classified under CWE-244. CVSS score: 8.6/10. Published 2026-03-04.
How severe is CVE-2026-20039?: High severity. CVSS v3 base score is 8.6 out of 10.