CVE-2026-20135: CWE-415
Source GCVE Database
Not known to be exploited · CVSS 8.6 High.
Data as of 31 Oct 2026, 20:20 UTC
- EPSS
- 0.6% chance of exploitation in 30 days – higher than 51% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:HExploitation evidence
Disclosed: evidence found.
CVE published 16 Sep 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 31 Oct 2026.
What to do
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| CiscoCisco Secure Firewall Threat Defense (FTD) Software | Affected
| Fixed in– |
AI-suggested
Until a patch is available, monitor for unusual TLS 1.3 traffic and consider limiting exposure of TLS 1.3-enabled listening sockets if feasible.
Description
A vulnerability in the TLS 1.3 implementation of Cisco Secure Firewall Threat Defense (FTD) Software allows an unauthenticated remote attacker to cause the device to reload unexpectedly, resulting in a denial of service (DoS). The issue arises from improper buffer management during TLS 1.3 connections. Exploitation involves sending a crafted TLS 1.3 packet to a TLS 1.3-enabled listening socket, causing the LINA process to crash and the device to reload either before or after connection authentication.