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CVE-2026-20039

HIGHCVSS 8.6/10EPSS 0.36%

Last modified

CVE-2026-20039 is a high-severity vulnerability rated 8.6/10 on the CVSS scale. 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. EPSS estimates a 0.36% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1
8.6/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

EPSS Probability
0.36%

28.7th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

VendorProductVersions
CiscoAdaptive Security Appliance Software>= 9.12.1, < 9.16.4.84
CiscoAdaptive Security Appliance Software>= 9.17.1, < 9.18.4.57
CiscoAdaptive Security Appliance Software>= 9.19.1, < 9.20.3.16
CiscoAdaptive Security Appliance Software>= 9.22.1.1, < 9.22.2.4
CiscoAdaptive Security Appliance Software>= 9.23.1, < 9.23.1.3
CiscoSecure Firewall Threat Defense>= 6.4.0, < 7.0.9
CiscoSecure Firewall Threat Defense>= 7.1.0, < 7.2.10
CiscoSecure Firewall Threat Defense>= 7.3.0, < 7.4.3
CiscoSecure Firewall Threat Defense>= 7.6.0, < 7.6.1
CiscoSecure Firewall Threat Defense>= 7.7.0, < 7.7.10

References

Timeline

Published
Last Modified
Status
Analyzed

Frequently Asked Questions

What is CVE-2026-20039?
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&nbsp;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.
How severe is CVE-2026-20039?
CVE-2026-20039 has a CVSS score of 8.6/10 (HIGH severity). The EPSS model estimates a 0.36% probability of exploitation in the next 30 days.
How do I fix CVE-2026-20039?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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Source: NVD / NIST