CVE-2026-20039
Memory Management DoS in Cisco ASA and FTD VPN Web Server
Publication date: 2026-03-04
Last updated on: 2026-04-16
Assigner: Cisco Systems, Inc.
Description
Description
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 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. |
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?
This vulnerability exists in the VPN web server component of Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software.
It is caused by ineffective memory management in the VPN web server, which can be exploited by an unauthenticated, remote attacker.
The attacker can send a large number of specially crafted HTTP requests to the affected device, which may cause the device to reload unexpectedly.
This results in a denial of service (DoS) condition, making the device temporarily unavailable.
How can this vulnerability impact me? :
The primary impact of this vulnerability is a denial of service (DoS) condition on the affected device.
An attacker exploiting this vulnerability can cause the device to reload, disrupting normal operations and potentially causing network downtime.
This can affect availability of VPN services and network security functions provided by the Cisco Secure Firewall devices.
How does this vulnerability affect compliance with common standards and regulations (like GDPR, HIPAA)?:
I don't know
How can this vulnerability be detected on my network or system? Can you suggest some commands?
I don't know
What immediate steps should I take to mitigate this vulnerability?
I don't know