CVE-2026-20135
published 2026-09-16CVE-2026-20135: A vulnerability in the TLS 1.3 implementation in Cisco Secure Firewall Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause…
PriorityP353high8.6CVSS 3.1
AVNACLPRNUINSCCNINAH
EPSS
0.46%
38.7th percentile
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
58 ranges· showing 25
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| cisco | cisco_secure_firewall_threat_defense_software | — | — |
| cisco | cisco_secure_firewall_threat_defense_software | — | — |
| cisco | cisco_secure_firewall_threat_defense_software | — | — |
| cisco | cisco_secure_firewall_threat_defense_software | — | — |
| cisco | cisco_secure_firewall_threat_defense_software | — | — |
| cisco | cisco_secure_firewall_threat_defense_software | — | — |
| cisco | cisco_secure_firewall_threat_defense_software | — | — |
| cisco | cisco_secure_firewall_threat_defense_software | — | — |
| cisco | cisco_secure_firewall_threat_defense_software | — | — |
| cisco | cisco_secure_firewall_threat_defense_software | — | — |
| cisco | cisco_secure_firewall_threat_defense_software | — | — |
| cisco | cisco_secure_firewall_threat_defense_software | — | — |
| cisco | cisco_secure_firewall_threat_defense_software | — | — |
| cisco | cisco_secure_firewall_threat_defense_software | — | — |
| cisco | cisco_secure_firewall_threat_defense_software | — | — |
| cisco | cisco_secure_firewall_threat_defense_software | — | — |
| cisco | cisco_secure_firewall_threat_defense_software | — | — |
| cisco | cisco_secure_firewall_threat_defense_software | — | — |
| cisco | cisco_secure_firewall_threat_defense_software | — | — |
| cisco | cisco_secure_firewall_threat_defense_software | — | — |
| cisco | cisco_secure_firewall_threat_defense_software | — | — |
| cisco | cisco_secure_firewall_threat_defense_software | — | — |
| cisco | cisco_secure_firewall_threat_defense_software | — | — |
| cisco | cisco_secure_firewall_threat_defense_software | — | — |
| cisco | cisco_secure_firewall_threat_defense_software | — | — |
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VulDB
Cisco Secure Firewall Threat Defense up to 7.7.11 TLS 1.3 Implementation denial of service
vuldb·2026-09-16·CVSS 8.6
CVE-2026-20135 [HIGH] Cisco Secure Firewall Threat Defense up to 7.7.11 TLS 1.3 Implementation denial of service
A vulnerability labeled as critical has been found in Cisco Secure Firewall Threat Defense. The affected element is an unknown function of the component TLS 1.3 Implementation. Executing a manipulation can lead to denial of service.
This vulnerability is tracked as CVE-2026-20135. The attack can be launched remotely. No exploit exists.
The affected component should be upgraded.
GHSA
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,
ghsa_unreviewed·2026-09-16
CVE-2026-20135 [HIGH] CWE-415 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,
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.
No detection rules found.
No public exploits indexed.
No writeups or analysis indexed.
2026-09-16
Published