#VU123550 Input validation error in Cisco Secure Firewall Management Center (formerly Firepower Management Center, FMC) and Cisco Firewall Threat Defense (FTD) - CVE-2026-20066

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Main Vulnerability Database Vulnerabilities #VU123550

#VU123550 Input validation error in Cisco Secure Firewall Management Center (formerly Firepower Management Center, FMC) and Cisco Firewall Threat Defense (FTD) - CVE-2026-20066

Published: March 4, 2026


Vulnerability identifier: #VU123550
Vulnerability risk: Medium
CVSSv4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:U/U:Green
CVE-ID: CVE-2026-20066
CWE-ID: CWE-20
Exploitation vector: Remote access
Exploit availability: No public exploit available
Vulnerable software:
Cisco Secure Firewall Management Center (formerly Firepower Management Center, FMC)
Cisco Firewall Threat Defense (FTD)
Software vendor:
Cisco Systems, Inc

Description

The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.

The vulnerability exists due to an error in the JSTokenizer normalization logic when the HTTP inspection normalizes JavaScript. A remote attacker can send specially crafted HTTP packets through an established connection that is parsed by Snort 3 and perform a denial of service attack.


Remediation

Install updates from vendor's website.

External links