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CVE-2026-20135highCWE-415

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

21Vexday Risk Score

No sign of exploitation. No public exploitation artifact known so far.

ssvc Trackcvss 8.6epss 0.5%
exploitation probability
0.5%top 61% of all CVEs
observed exploitation
nono source reports it
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:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H