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5.8
Cisco FTD Software May Crash if Sent a Malicious TLS Packet
CVE-2026-20006
Summary
A flaw in Cisco's FTD software could cause it to crash if it receives a specially crafted packet. This could lead to network outages, disrupting business operations. To protect against this, update your FTD software as soon as possible.
Original title
A vulnerability in the TLS cryptography functionality of the Snort 3 Detection Engine of Cisco Secure Firewall Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause...
Original description
A vulnerability in the TLS cryptography functionality of the Snort 3 Detection Engine of Cisco Secure Firewall Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause the Snort 3 Detection Engine to unexpectedly restart, resulting in a denial of service (DoS) condition.
This vulnerability is due to improper implementation of the TLS protocol. An attacker could exploit this vulnerability by sending a crafted TLS packet to an affected system. A successful exploit could allow the attacker to cause a device that is running Cisco Secure FTD Software to drop network traffic, resulting in a DoS condition.
Note: TLS 1.3 is not affected by this vulnerability.
This vulnerability is due to improper implementation of the TLS protocol. An attacker could exploit this vulnerability by sending a crafted TLS packet to an affected system. A successful exploit could allow the attacker to cause a device that is running Cisco Secure FTD Software to drop network traffic, resulting in a DoS condition.
Note: TLS 1.3 is not affected by this vulnerability.
nvd CVSS3.1
5.8
Vulnerability type
CWE-388
Published: 4 Mar 2026 · Updated: 13 Mar 2026 · First seen: 6 Mar 2026