High 8.6Published Mar 4, 2026

CVE-2026-20039Cisco Adaptive Security Appliance and Firepower Threat Defense Software SSL VPN Authentication Denial of Service Vulnerability

Updated under an hour ago (Oct 27, 2026, 8:25 PM ET)

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It affects Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and 3 other products. Add what you run to find out whether that includes you.

No exploitation reported and no EPSS estimate yet.

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Every CVE for Cisco Secure Firewall Adaptive Security Appliance (ASA) Software

Exploited in the last 30 days

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.

CVSS: 8.6 HIGH (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
Weakness (CWE): CWE-244
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: cisco
NVD analysis: Analyzed
Record last updated: Mar 5, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

Cisco Cisco Secure Firewall Adaptive Security Appliance (ASA) Software cisco:secure_firewall_adaptive_security_appliance_asa_software (from the name)	9.12.3; 9.12.1; 9.12.2; 9.12.4; 9.12.3.2; 9.12.3.7; 9.12.2.5; 9.12.3.12; and 134 more ranges	CNA record
Cisco Cisco Secure Firewall Threat Defense (FTD) Software cisco:secure_firewall_threat_defense_ftd_software (from the name)	6.4.0.1; 6.4.0.2; 6.4.0.5; 6.4.0; 6.4.0.3; 6.4.0.4; 6.4.0.6; 6.4.0.7; and 60 more ranges	CNA record
cisco adaptive_security_appliance_software cisco:adaptive_security_appliance_software	from 9.12.1 before 9.16.4.84; from 9.17.1 before 9.18.4.57; from 9.19.1 before 9.20.3.16; from 9.22.1.1 before 9.22.2.4; from 9.23.1 before 9.23.1.3	NVD
cisco secure_firewall_threat_defense cisco:secure_firewall_threat_defense	from 6.4.0 before 7.0.9; from 7.1.0 before 7.2.10; from 7.3.0 before 7.4.3; from 7.6.0 before 7.6.1; from 7.7.0 before 7.7.10	NVD

References

References

https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-vpn-dos-SpOFF2Re	vendor-advisory

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.