PatchSiren

PatchSiren cyber security CVE debrief

CVE-2026-20039 Cisco CVE debrief

AI-assisted PatchSiren debrief based on the supplied source corpus. The CVE record was published on 2026-03-04T18:16:17.140Z and has not been modified since then. This vulnerability affects Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software, allowing an unauthenticated, remote attacker to cause a denial of service (DoS) condition due to ineffective memory management of the VPN web server. An attacker could exploit this by sending crafted HTTP requests, potentially causing the device to reload. Organizations should review and apply patches, implement compensating controls, monitor logs, verify inventory, and restrict access to VPN web servers.

Vendor
Cisco
Product
Cisco Secure Firewall Adaptive Security Appliance (ASA) Software
CVSS
HIGH 8.6
CISA KEV
Not listed in stored evidence
Original CVE published
2026-03-04
Original CVE updated
2026-08-11
Advisory published
2026-03-04
Advisory updated
2026-08-11

Who should care

Organizations using Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software should be aware of this vulnerability and take steps to mitigate it.

Technical summary

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.

Defensive priority

Organizations using Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software should prioritize patching to prevent potential denial of service (DoS) attacks.

Recommended defensive actions

  • Review and apply patches for Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software
  • Implement compensating controls such as rate limiting on HTTP requests to VPN web servers
  • Monitor VPN web server logs for unusual traffic patterns
  • Verify and update inventory of Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software
  • Restrict access to VPN web servers to only necessary personnel

Evidence notes

The vulnerability is due to ineffective memory management of the VPN web server in Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software. An attacker could exploit this vulnerability by sending a large number of crafted HTTP requests to an affected device, potentially causing the device to reload and resulting in a DoS condition.

Official resources

AI-assisted PatchSiren debrief based on the supplied source corpus. The CVE record was published on 2026-03-04T18:16:17.140Z and has not been modified since then.