CVE-2026-20135 PUBLISHED

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

Assigner: cisco
Reserved: 08.10.2025 Published: 16.09.2026 Updated: 16.09.2026

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.

Metrics

CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
CVSS Score: 8.6

Product Status

Vendor Cisco
Product Cisco Secure Firewall Threat Defense (FTD) Software
Versions Default: unknown
  • Version 7.0.0 is affected
  • Version 7.0.0.1 is affected
  • Version 7.0.1 is affected
  • Version 7.0.1.1 is affected
  • Version 7.0.2 is affected
  • Version 7.2.0 is affected
  • Version 7.0.2.1 is affected
  • Version 7.0.3 is affected
  • Version 7.2.0.1 is affected
  • Version 7.0.4 is affected
  • Version 7.2.1 is affected
  • Version 7.0.5 is affected
  • Version 7.3.0 is affected
  • Version 7.2.2 is affected
  • Version 7.2.3 is affected
  • Version 7.3.1 is affected
  • Version 7.2.4 is affected
  • Version 7.0.6 is affected
  • Version 7.2.5 is affected
  • Version 7.2.4.1 is affected
  • Version 7.3.1.1 is affected
  • Version 7.4.0 is affected
  • Version 7.0.6.1 is affected
  • Version 7.2.5.1 is affected
  • Version 7.4.1 is affected
  • Version 7.2.6 is affected
  • Version 7.0.6.2 is affected
  • Version 7.4.1.1 is affected
  • Version 7.2.7 is affected
  • Version 7.2.5.2 is affected
  • Version 7.3.1.2 is affected
  • Version 7.2.8 is affected
  • Version 7.6.0 is affected
  • Version 7.4.2 is affected
  • Version 7.2.8.1 is affected
  • Version 7.0.6.3 is affected
  • Version 7.4.2.1 is affected
  • Version 7.2.9 is affected
  • Version 7.0.7 is affected
  • Version 7.7.0 is affected
  • Version 7.4.2.2 is affected
  • Version 7.2.10 is affected
  • Version 7.6.1 is affected
  • Version 7.4.2.3 is affected
  • Version 7.0.8 is affected
  • Version 7.6.2 is affected
  • Version 7.7.10 is affected
  • Version 7.7.11 is affected
  • Version 7.0.8.1 is affected
  • Version 7.6.2.1 is affected
  • Version 7.7.10.1 is affected
  • Version 7.4.2.4 is affected
  • Version 7.2.10.2 is affected
  • Version 7.4.3 is affected
  • Version 7.6.4 is affected
  • Version 7.4.4 is affected
  • Version 7.0.9 is affected
  • Version 7.2.11 is affected

Exploits

The Cisco Product Security Incident Response Team (PSIRT) is not aware of any public announcements or malicious use of the vulnerability that is described in this advisory.

References

Problem Types

  • Double Free cwe