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Cisco Secure Firewall Threat Defense Software TLS 1.3 Denial of Service Vulnerability

CVSS 3.1 8.6 HIGHCheck source for fixed versionsKEV status unknown

cve-program · CVE-2026-20135

Published

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.

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CVE-2026-20135 · CVE overview and exploitation status

cve-program · CVE-2026-20135

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Sources read 13 Nov 08:15 UTC · 274 of 275 readable · 272 fully read · documentation 469/469 current