CVE-2026-20135: Cisco Secure Firewall Threat Defense Software TLS 1.3 Denial of Service Vulnerability
Cisco · Cisco Secure Firewall Threat Defense (FTD) Software
Affected: Cisco Secure Firewall Threat Defense (FTD) Software · Exploitation: unlikely (under 1%)
Not in CyberSIXT coverage yet: no article names this CVE. This page shows the public record.
Higher than 52% of scored CVEs
DescriptionCVE.org
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 products1
From the CVE record. A product or version that is not listed is unknown, not unaffected.
- Cisco · Cisco Secure Firewall Threat Defense (FTD) Software7.0.0; 7.0.0.1; 7.0.1; 7.0.1.1; 7.0.2; 7.2.0 and 52 more
On the Atlas
Every published CVE is on the CyberSIXT Atlas, grouped by weakness, vendor and month.
- Exploitation
- Unlikely (under 1%). EPSS under 1%, or no score yet.
- CISA KEV
- Not listed
- Public check
- No public nuclei template
- Weakness
- Double Free · Memory Corruption
- Vendor
- Cisco
- Published
- September 2026
CoverageNo articles yet
No CyberSIXT article names CVE-2026-20135 yet, so there is no coverage timeline, action brief or change log for it. Everything on this page comes from the public CVE record, CISA KEV, EPSS and the nuclei template index. Search the archive or see the CVEs in the news.