CVE-2026-20039

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

View on CVE.org

Published Mar 4, 2026 CVSS 3.1 · 8.6 High EPSS < 1% KEV · Not listed

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.

Affected Products

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions

Cisco

Cisco Secure Firewall Adaptive Security Appliance (ASA) Software

unknown

Version	Status	Constraints
`9.12.3`	affected	—
`9.12.1`	affected	—
`9.12.2`	affected	—
`9.12.4`	affected	—
`9.12.3.2`	affected	—
`9.12.3.7`	affected	—
`9.12.2.5`	affected	—
`9.12.3.12`	affected	—
`9.12.1.3`	affected	—
`9.12.2.4`	affected	—
`9.12.1.2`	affected	—
`9.12.2.9`	affected	—
`9.12.3.9`	affected	—
`9.12.2.1`	affected	—
`9.12.4.2`	affected	—
`9.12.4.4`	affected	—
`9.12.4.7`	affected	—
`9.12.4.8`	affected	—
`9.12.4.10`	affected	—
`9.12.4.13`	affected	—
`9.12.4.18`	affected	—
`9.12.4.24`	affected	—
`9.16.1`	affected	—
`9.12.4.26`	affected	—
`9.16.1.28`	affected	—
`9.12.4.29`	affected	—
`9.16.2`	affected	—
`9.12.4.30`	affected	—
`9.16.2.3`	affected	—
`9.12.4.35`	affected	—
`9.16.2.7`	affected	—
`9.12.4.37`	affected	—
`9.17.1`	affected	—
`9.16.2.11`	affected	—
`9.16.2.13`	affected	—
`9.12.4.39`	affected	—
`9.12.4.38`	affected	—
`9.16.2.14`	affected	—
`9.17.1.7`	affected	—
`9.12.4.40`	affected	—
`9.16.3.3`	affected	—
`9.16.3`	affected	—
`9.16.3.14`	affected	—
`9.17.1.9`	affected	—
`9.12.4.41`	affected	—
`9.17.1.10`	affected	—
`9.18.1`	affected	—
`9.12.4.47`	affected	—
`9.16.3.15`	affected	—
`9.18.1.3`	affected	—
`9.17.1.11`	affected	—
`9.12.4.48`	affected	—
`9.18.2`	affected	—
`9.16.3.19`	affected	—
`9.17.1.13`	affected	—
`9.12.4.50`	affected	—
`9.17.1.15`	affected	—
`9.12.4.52`	affected	—
`9.16.3.23`	affected	—
`9.18.2.5`	affected	—
`9.16.4`	affected	—
`9.12.4.54`	affected	—
`9.17.1.20`	affected	—
`9.18.2.7`	affected	—
`9.19.1`	affected	—
`9.16.4.9`	affected	—
`9.12.4.55`	affected	—
`9.18.2.8`	affected	—
`9.16.4.14`	affected	—
`9.18.3`	affected	—
`9.19.1.5`	affected	—
`9.12.4.56`	affected	—
`9.17.1.30`	affected	—
`9.19.1.9`	affected	—
`9.18.3.39`	affected	—
`9.16.4.19`	affected	—
`9.12.4.58`	affected	—
`9.19.1.12`	affected	—
`9.18.3.46`	affected	—
`9.16.4.27`	affected	—
`9.19.1.18`	affected	—
`9.18.3.53`	affected	—
`9.18.3.55`	affected	—
`9.16.4.38`	affected	—
`9.17.1.33`	affected	—
`9.12.4.62`	affected	—
`9.16.4.39`	affected	—
`9.18.3.56`	affected	—
`9.20.1`	affected	—
`9.16.4.42`	affected	—
`9.19.1.22`	affected	—
`9.18.4`	affected	—
`9.20.1.5`	affected	—
`9.18.4.5`	affected	—
`9.19.1.24`	affected	—
`9.16.4.48`	affected	—
`9.18.4.8`	affected	—
`9.20.2`	affected	—
`9.19.1.27`	affected	—
`9.12.4.65`	affected	—
`9.16.4.55`	affected	—
`9.18.4.22`	affected	—
`9.20.2.10`	affected	—
`9.16.4.57`	affected	—
`9.19.1.28`	affected	—
`9.17.1.39`	affected	—
`9.12.4.67`	affected	—
`9.18.4.24`	affected	—
`9.20.2.21`	affected	—
`9.16.4.61`	affected	—
`9.19.1.31`	affected	—
`9.18.4.29`	affected	—
`9.20.2.22`	affected	—
`9.16.4.62`	affected	—
`9.18.4.34`	affected	—
`9.20.3`	affected	—
`9.16.4.67`	affected	—
`9.16.4.70`	affected	—
`9.18.4.40`	affected	—
`9.23.1`	affected	—
`9.22.1.1`	affected	—
`9.16.4.71`	affected	—
`9.20.3.4`	affected	—
`9.18.4.47`	affected	—
`9.20.3.7`	affected	—
`9.17.1.45`	affected	—
`9.19.1.37`	affected	—
`9.17.1.46`	affected	—
`9.16.4.76`	affected	—
`9.20.3.9`	affected	—
`9.19.1.38`	affected	—
`9.18.4.50`	affected	—
`9.22.1.3`	affected	—
`9.20.3.10`	affected	—
`9.22.1.2`	affected	—
`9.18.4.52`	affected	—
`9.20.3.13`	affected	—
`9.22.1.6`	affected	—
`9.18.4.53`	affected	—
`9.16.4.82`	affected	—
`9.22.2`	affected	—
`9.19.1.42`	affected	—

Cisco

Cisco Secure Firewall Threat Defense (FTD) Software

unknown

Version	Status	Constraints
`6.4.0.1`	affected	—
`6.4.0.2`	affected	—
`6.4.0.5`	affected	—
`6.4.0`	affected	—
`6.4.0.3`	affected	—
`6.4.0.4`	affected	—
`6.4.0.6`	affected	—
`6.4.0.7`	affected	—
`6.4.0.8`	affected	—
`6.4.0.9`	affected	—
`6.4.0.10`	affected	—
`6.4.0.11`	affected	—
`6.4.0.12`	affected	—
`7.0.0`	affected	—
`7.0.0.1`	affected	—
`7.0.1`	affected	—
`7.1.0`	affected	—
`6.4.0.13`	affected	—
`7.0.1.1`	affected	—
`6.4.0.14`	affected	—
`7.1.0.1`	affected	—
`7.0.2`	affected	—
`6.4.0.15`	affected	—
`7.2.0`	affected	—
`7.0.2.1`	affected	—
`7.0.3`	affected	—
`7.1.0.2`	affected	—
`7.2.0.1`	affected	—
`7.0.4`	affected	—
`7.2.1`	affected	—
`7.0.5`	affected	—
`6.4.0.16`	affected	—
`7.3.0`	affected	—
`7.2.2`	affected	—
`7.2.3`	affected	—
`7.3.1`	affected	—
`7.1.0.3`	affected	—
`7.2.4`	affected	—
`7.0.6`	affected	—
`7.2.5`	affected	—
`7.2.4.1`	affected	—
`7.3.1.1`	affected	—
`7.4.0`	affected	—
`6.4.0.17`	affected	—
`7.0.6.1`	affected	—
`7.2.5.1`	affected	—
`7.4.1`	affected	—
`7.2.6`	affected	—
`7.0.6.2`	affected	—
`7.4.1.1`	affected	—
`6.4.0.18`	affected	—
`7.2.7`	affected	—
`7.2.5.2`	affected	—
`7.3.1.2`	affected	—
`7.2.8`	affected	—
`7.6.0`	affected	—
`7.4.2`	affected	—
`7.2.8.1`	affected	—
`7.0.6.3`	affected	—
`7.4.2.1`	affected	—
`7.2.9`	affected	—
`7.0.7`	affected	—
`7.7.0`	affected	—
`7.4.2.2`	affected	—
`7.4.2.3`	affected	—
`7.0.8`	affected	—
`7.0.8.1`	affected	—
`7.4.2.4`	affected	—

Configuration 1 [-]

OR	cpe:2.3:o:cisco:adaptive_security_appliance_software::::::::
	cpe:2.3:o:cisco:adaptive_security_appliance_software::::::::
	cpe:2.3:o:cisco:adaptive_security_appliance_software::::::::
	cpe:2.3:o:cisco:adaptive_security_appliance_software::::::::
	cpe:2.3:o:cisco:adaptive_security_appliance_software::::::::

Configuration 2 [-]

OR	cpe:2.3:a:cisco:secure_firewall_threat_defense::::::::
	cpe:2.3:a:cisco:secure_firewall_threat_defense::::::::
	cpe:2.3:a:cisco:secure_firewall_threat_defense::::::::
	cpe:2.3:a:cisco:secure_firewall_threat_defense::::::::
	cpe:2.3:a:cisco:secure_firewall_threat_defense::::::::

No data.

Vendor Product Versions

Cisco

Adaptive Security Appliance Software

Version	Status	Scheme	Platform
`9.12.3`	affected	semver	—
`9.12.1`	affected	semver	—
`9.12.2`	affected	semver	—
`9.12.4`	affected	semver	—
`9.12.3.2`	affected	generic	—
`9.12.3.7`	affected	generic	—
`9.12.2.5`	affected	generic	—
`9.12.3.12`	affected	generic	—
`9.12.1.3`	affected	generic	—
`9.12.2.4`	affected	generic	—
`9.12.1.2`	affected	generic	—
`9.12.2.9`	affected	generic	—
`9.12.3.9`	affected	generic	—
`9.12.2.1`	affected	generic	—
`9.12.4.2`	affected	generic	—
`9.12.4.4`	affected	generic	—
`9.12.4.7`	affected	generic	—
`9.12.4.8`	affected	generic	—
`9.12.4.10`	affected	generic	—
`9.12.4.13`	affected	generic	—
`9.12.4.18`	affected	generic	—
`9.12.4.24`	affected	generic	—
`9.16.1`	affected	semver	—
`9.12.4.26`	affected	generic	—
`9.16.1.28`	affected	generic	—
`9.12.4.29`	affected	generic	—
`9.16.2`	affected	semver	—
`9.12.4.30`	affected	generic	—
`9.16.2.3`	affected	generic	—
`9.12.4.35`	affected	generic	—
`9.16.2.7`	affected	generic	—
`9.12.4.37`	affected	generic	—
`9.17.1`	affected	semver	—
`9.16.2.11`	affected	generic	—
`9.16.2.13`	affected	generic	—
`9.12.4.39`	affected	generic	—
`9.12.4.38`	affected	generic	—
`9.16.2.14`	affected	generic	—
`9.17.1.7`	affected	semver	—
`9.12.4.40`	affected	generic	—
`9.16.3.3`	affected	generic	—
`9.16.3`	affected	semver	—
`9.16.3.14`	affected	generic	—
`9.17.1.9`	affected	generic	—
`9.12.4.41`	affected	generic	—
`9.17.1.10`	affected	generic	—
`9.18.1`	affected	semver	—
`9.12.4.47`	affected	generic	—
`9.16.3.15`	affected	generic	—
`9.18.1.3`	affected	semver	—
`9.17.1.11`	affected	generic	—
`9.12.4.48`	affected	generic	—
`9.18.2`	affected	semver	—
`9.16.3.19`	affected	generic	—
`9.17.1.13`	affected	generic	—
`9.12.4.50`	affected	generic	—
`9.17.1.15`	affected	generic	—
`9.12.4.52`	affected	generic	—
`9.16.3.23`	affected	generic	—
`9.18.2.5`	affected	generic	—
`9.16.4`	affected	semver	—
`9.12.4.54`	affected	generic	—
`9.17.1`	affected	semver	—
`9.18.2.7`	affected	generic	—
`9.19.1`	affected	semver	—
`9.16.4.9`	affected	generic	—
`9.12.4.55`	affected	generic	—
`9.18.2.8`	affected	generic	—
`9.16.4.14`	affected	generic	—
`9.18.3`	affected	semver	—
`9.19.1.5`	affected	generic	—
`9.12.4.56`	affected	generic	—
`9.17.1.30`	affected	generic	—
`9.19.1.9`	affected	generic	—
`9.18.3.39`	affected	generic	—
`9.16.4.19`	affected	generic	—
`9.12.4.58`	affected	generic	—
`9.19.1.12`	affected	generic	—
`9.18.3.46`	affected	generic	—
`9.16.4.27`	affected	generic	—
`9.19.1.18`	affected	generic	—
`9.18.3.53`	affected	generic	—
`9.18.3.55`	affected	generic	—
`9.16.4.38`	affected	generic	—
`9.17.1`	affected	generic	—
`9.18.3.56`	affected	generic	—
`9.20.1`	affected	semver	—
`9.16.4.42`	affected	generic	—
`9.19.1`	affected	semver	—
`9.18.4`	affected	generic	—
`9.20.1`	affected	semver	—
`9.18.4.5`	affected	generic	—
`9.19.1.24`	affected	generic	—
`9.16.4.48`	affected	generic	—
`9.18.4.8`	affected	generic	—
`9.20.2`	affected	semver	—
`9.19.1.27`	affected	generic	—
`9.12.4.65`	affected	generic	—
`9.16.4.55`	affected	generic	—
`9.18.4.22`	affected	generic	—
`9.20.2`	affected	semver	—
`9.16.4.57`	affected	generic	—
`9.19.1.28`	affected	generic	—
`9.17.1`	affected	generic	—

Cisco

Secure Firewall Threat Defense

Version	Status	Scheme	Platform
`6.4.0.1`	affected	generic	—
`6.4.0.2`	affected	generic	—
`6.4.0.5`	affected	generic	—
`6.4.0`	affected	generic	—
`6.4.0.3`	affected	generic	—
`6.4.0.4`	affected	generic	—
`6.4.0.6`	affected	generic	—
`6.4.0.7`	affected	generic	—
`6.4.0.8`	affected	generic	—
`6.4.0.9`	affected	generic	—
`6.4.0.10`	affected	generic	—
`6.4.0.11`	affected	generic	—
`6.4.0.12`	affected	generic	—
`7.0.0`	affected	semver	—
`7.0.0.1`	affected	generic	—
`7.0.1`	affected	semver	—
`7.1.0`	affected	semver	—
`6.4.0.13`	affected	generic	—
`7.0.1.1`	affected	generic	—
`6.4.0.14`	affected	generic	—
`7.1.0.1`	affected	semver	—
`7.0.2`	affected	generic	—
`6.4.0.15`	affected	generic	—
`7.2.0`	affected	semver	—
`7.0.2.1`	affected	generic	—
`7.0.3`	affected	generic	—
`7.1.0.2`	affected	generic	—
`7.2.0.1`	affected	semver	—
`7.3.1`	affected	generic	—
`7.1.0.3`	affected	generic	—
`7.2.4`	affected	generic	—
`7.0.6`	affected	generic	—
`6.4.0.16`	affected	generic	—
`7.3.0`	affected	generic	—
`7.2.2`	affected	generic	—
`7.2.3`	affected	generic	—
`7.3.1.1`	affected	generic	—
`7.1.0.1`	affected	semver	—
`7.2.0.1`	affected	semver	—
`7.2.1`	affected	semver	—
`7.0.4`	affected	generic	—
`7.4.0`	affected	semver	—
`6.4.0.18`	affected	generic	—
`7.2.7`	affected	generic	—
`7.2.5.2`	affected	generic	—
`7.3.1.2`	affected	generic	—
`7.2.8`	affected	generic	—
`7.6.0`	affected	semver	—
`7.4.2`	affected	semver	—
`7.2.8.1`	affected	generic	—
`7.0.6.3`	affected	generic	—
`7.4.2.1`	affected	generic	—
`7.2.9`	affected	generic	—
`7.0.7`	affected	generic	—
`7.7.0`	affected	semver	—
`7.4.2.2`	affected	generic	—
`7.4.2.3`	affected	generic	—
`7.0.8`	affected	generic	—
`7.0.8.1`	affected	generic	—
`7.4.2.4`	affected	generic	—
`7.2.5`	affected	generic	—
`7.2.4.1`	affected	generic	—
`7.2.6`	affected	generic	—
`7.4.1`	affected	generic	—
`7.4.1.1`	affected	generic	—
`7.2.5`	affected	generic	—
`7.4.1.1`	affected	generic	—
`7.2.5`	affected	generic	—
`7.2.5`	affected	generic	—
`7.4.1`	affected	generic	—
`7.6.0`	affected	semver	—
`7.7.0`	affected	semver	—

Remediation

No solution or workaround provided in the CVE record

Tracking

Advisories

No advisories available

Metrics

No CVSS v4.0

Attack Vector Network

Attack Complexity Low

Privileges Required None

Scope Changed

Confidentiality Impact None

Integrity Impact None

Availability Impact High

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

Exploit prediction score: < 1% (0.411% probability within 30 days)

Exploitation none

Automatable yes

Technical Impact partial

References

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

History

Aug 11, 2026 8:00 PM Affected versions updated. Affected vendors updated View changes

Type	Values Removed	Values Added
CPEs	cpe:2.3:a:cisco:firepower_threat_defense_software::::::::	cpe:2.3:a:cisco:secure_firewall_threat_defense::::::::
Vendors & Products	Cisco firepower Threat Defense Software

Apr 16, 2026 8:15 PM First appearance in the feed. Affected versions updated. Affected vendors updated View changes

Type	Values Removed	Values Added
First Time appeared		Cisco firepower Threat Defense Software
CPEs		cpe:2.3:a:cisco:firepower_threat_defense_software:::::::: cpe:2.3:o:cisco:adaptive_security_appliance_software::::::::
Vendors & Products		Cisco firepower Threat Defense Software

Mar 5, 2026 4:15 PM Scoring metrics updated View changes

Type	Values Removed	Values Added
Metrics		ssvc `{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}`

Mar 5, 2026 9:15 AM First appearance in the feed. Affected vendors updated View changes

Type	Values Removed	Values Added
First Time appeared		Cisco Cisco adaptive Security Appliance Software Cisco secure Firewall Threat Defense
Vendors & Products		Cisco Cisco adaptive Security Appliance Software Cisco secure Firewall Threat Defense

Mar 4, 2026 5:30 PM Description updated. Title updated. Weaknesses updated. Added references. Scoring metrics updated View changes

Type	Values Removed	Values Added
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.
Title		Cisco Adaptive Security Appliance and Firepower Threat Defense Software SSL VPN Authentication Denial of Service Vulnerability
Weaknesses		CWE-244
References		https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-vpn-dos-SpOFF2Re
Metrics		cvssV3_1 `{'score': 8.6, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H'}`