Input validation error in Cisco Firewall Threat Defense (FTD) and Cisco Secure Firewall Management Center (formerly Firepower Management Center, FMC) - CVE-2026-20066
Published: March 4, 2026
Vulnerability identifier: #VU123550
CSH Severity: Medium
CVSS v4: 6.9 [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]
CVE-ID: CVE-2026-20066
CWE-ID: CWE-20
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
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.
Affected software
Cisco Firewall Threat Defense (FTD)
Cisco Secure Firewall Management Center (formerly Firepower Management Center, FMC)
Cisco Secure Firewall Management Center (formerly Firepower Management Center, FMC)
How to mitigate CVE-2026-20066
Install updates from vendor's website.
Cisco Firewall Threat Defense (FTD) - addressed in versions 7.4.4, 7.6.4, 7.7.11
Cisco Secure Firewall Management Center (formerly Firepower Management Center, FMC) - addressed in versions 7.4.4, 7.6.4, 7.7.11
Cisco Secure Firewall Management Center (formerly Firepower Management Center, FMC) - addressed in versions 7.4.4, 7.6.4, 7.7.11