Vulnerability · Published Sep 16, 2026 · Assigned by cisco
CVE-2026-20135Cisco Secure Firewall Threat Defense Software TLS 1.3 Denial of Service Vulnerability
High 8.6
In plain English
A high-severity double free in Cisco Secure Firewall Threat Defense (FTD) Software from Cisco. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.7% (higher than 52% of all known vulnerabilities).
Official description
A vulnerability in the TLS 1.3 implementation in Cisco Secure Firewall Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause an affected device to reload unexpectedly, resulting in a denial of service (DoS) condition. This vulnerability is due to improper buffer management during the TLS 1.3 connection. An attacker could exploit this vulnerability by sending a crafted TLS 1.3 packet to an affected system through a TLS 1.3-enabled listening socket. A successful exploit could allow the attacker to cause the LINA process to crash, which would cause the device to reload. The reload can happen before or after authentication of the connection.Note: TLS 1.3 connections include both data traffic and user-management traffic.
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Cisco | Cisco Secure Firewall Threat Defense (FTD) Software | 7.0.07.0.0.17.0.17.0.1.17.0.27.2.07.0.2.17.0.3 |
Weakness: CWE-415 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H