High severity8.6NVD Advisory· Published Mar 4, 2026· Updated Apr 16, 2026

CVE-2026-20039

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.

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LLM-synthesized narrative grounded in this CVE's description and references.

Affected products

Cisco Systems, Inc./Firepower Threat Defense Software
cpe:2.3:a:cisco:firepower_threat_defense_software:*:*:*:*:*:*:*:*
Range: >=6.4.0,<7.0.9
Cisco Systems, Inc./Cisco Adaptive Security Appliance
cpe:2.3:o:cisco:adaptive_security_appliance_software:*:*:*:*:*:*:*:*
Range: >=9.12.1,<9.16.4.84
Cisco Systems, Inc./Adaptive Security Appliance Cx Context Aware Security Softwarellm-fuzzy
Cisco Systems, Inc./Cisco Secure Firewall Threat Defense (FTD) Softwarellm-fuzzy

Patches

Vulnerability mechanics

References

sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-vpn-dos-SpOFF2RenvdVendor Advisory

News mentions

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