CVE-2026-20100: cisco adaptive_security_appliance_software Classic Buffer Overflow

Vulnerability summary

CVE-2026-20100 is a high (CVSS 7.7) Classic Buffer Overflow vulnerability in cisco adaptive_security_appliance_software. EPSS estimates a 0.29% chance of exploitation in the next 30 days, higher than 20.5% of scored vulnerabilities.

Timeline

1. 04-03-2026
   PublishedVulnerability first disclosed.
2. 05-03-2026
   Last modifiedVulnerability information updated.

Description

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.

• CWE-120Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')The product copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer.