CVE-2026-20039
Received
Received - Intake
Memory Management DoS in Cisco ASA and FTD VPN Web Server
Vulnerability report for CVE-2026-20039, including description, CVSS score, EPSS score, affected products, exploitability, helpful resources, and attack-flow context.
Publication date: 2026-03-04
Last updated on: 2026-04-16
Assigner: Cisco Systems, Inc.
Description
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.
CVSS Scores
EPSS Scores
| Probability: | |
| Percentile: |
Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| cisco | adaptive_security_appliance_software | From 9.17.1 (inc) to 9.18.4.57 (exc) |
| cisco | adaptive_security_appliance_software | From 9.22.1.1 (inc) to 9.22.2.4 (exc) |
| cisco | adaptive_security_appliance_software | From 9.23.1 (inc) to 9.23.1.3 (exc) |
| cisco | adaptive_security_appliance_software | From 9.12.1 (inc) to 9.16.4.84 (exc) |
| cisco | adaptive_security_appliance_software | From 9.19.1 (inc) to 9.20.3.16 (exc) |
| cisco | firepower_threat_defense_software | From 6.4.0 (inc) to 7.0.9 (exc) |
| cisco | firepower_threat_defense_software | From 7.3.0 (inc) to 7.4.3 (exc) |
| cisco | firepower_threat_defense_software | From 7.7.0 (inc) to 7.7.10 (exc) |
| cisco | firepower_threat_defense_software | From 7.1.0 (inc) to 7.2.10 (exc) |
| cisco | firepower_threat_defense_software | From 7.6.0 (inc) to 7.6.1 (exc) |
Helpful Resources
Exploitability
CWE
KEV
| CWE ID | Description |
|---|---|
| CWE-244 | Using realloc() to resize buffers that store sensitive information can leave the sensitive information exposed to attack, because it is not removed from memory. |
