What is the CVSS score of CVE-2026-20100?

CVE-2026-20100 has a CVSS 3.1 base score of 7.7 (High). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H. EPSS exploitation probability: 0.2%.

Which versions of Adaptive Security Appliance Software are affected by CVE-2026-20100?

A denial-of-service vulnerability in Cisco Secure Firewall VPN components could allow authenticated remote attackers to crash VPN gateways, disrupting remote worker connectivity and business…

How to fix or mitigate CVE-2026-20100?

Within 24 hours: inventory all Cisco ASA and FTD devices using SSL VPN Remote Access; assess VPN user base and criticality. Within 7 days: implement network segmentation to restrict VPN access to authorized personnel only; enable enhanced monitoring/logging of VPN connections for anomalous LUA interpreter activity. Within 30 days: contact Cisco for patch availability status; prepare change management plan for immediate deployment upon patch release; evaluate alternative VPN solutions as contingency.

Adaptive Security Appliance Software CVE-2026-20100

HIGH

Classic Buffer Overflow (CWE-120)

2026-03-04 psirt@cisco.com

Buffer Overflow Denial Of Service Cisco Adaptive Security Appliance Software Firepower Threat Defense

7.7

CVSS 3.1 · Vendor: cisco

Severity by source

Vendor (cisco) PRIMARY

7.7 HIGH

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

Primary rating from Vendor (cisco) · only source for this CVE.

CVSS VectorVendor: cisco

Attack Vector

Network

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Changed

Confidentiality

None

Integrity

None

Availability

High

Lifecycle Timeline

Analysis Generated

Mar 12, 2026 - 22:05 vuln.today

CVE Published

Mar 04, 2026 - 18:16 nvd

HIGH 7.7

DescriptionCVE.org

A vulnerability in the LUA interperter of the Remote Access SSL VPN feature of Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Secure Firewall Threat Defense (FTD) Software could allow an authenticated, remote attacker with a valid VPN connection to cause the device to reload unexpectedly, resulting in a denial of service (DoS) condition. This does not affect the management or MUS interfaces. This vulnerability is due to trusting user input without validation in the LUA interprerter. An attacker could exploit this vulnerability by sending crafted HTTP packets to the Remote Access SSL VPN server. A successful exploit could allow the attacker to cause the device to reload, resulting in a DoS condition.

AnalysisAI

Cisco Secure Firewall ASA and FTD devices are vulnerable to a denial of service attack through the Remote Access SSL VPN feature, where authenticated attackers can trigger unvalidated input processing in the Lua interpreter to force device reloads. The vulnerability stems from insufficient input validation in the Lua interpreter and can be exploited by sending specially crafted HTTP packets over an existing VPN connection. No patch is currently available for this HIGH severity issue (CVSS 7.7).

Technical ContextAI

Classified as CWE-120 (Classic Buffer Overflow). A vulnerability in the LUA interperter of the Remote Access SSL VPN feature of Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Secure Firewall Threat Defense (FTD) Software could allow an authenticated, remote attacker with a valid VPN connection to cause the device to reload unexpectedly, resulting in a denial of service (DoS) condition. This does not affect the management or MUS interfaces. This vulnerability is due to trusting user input without validation in the LUA i

RemediationAI

Monitor vendor advisories for a patch. Enable ASLR, DEP/NX, and stack canaries where possible. Restrict network access to the affected service where possible.