Vulnerability 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.
CVSS Score
HIGH
Related Weaknesses (CWE)
References
FAQ
What is CVE-2026-20135?
CVE-2026-20135 is a vulnerability with a CVSS score of 8.6 (HIGH). 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,...
How severe is CVE-2026-20135?
CVE-2026-20135 has been rated HIGH with a CVSS base score of 8.6/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-20135?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.