8.6

CVE-2026-20135: cisco cisco secure firewall threat defense (ftd) software Double Free

CVSS: 8.6v3.1HighAwaiting analysis
Published 16-09-2026Last modified 17-09-2026
Open JSON

Vulnerability summary

CVE-2026-20135 is a high (CVSS 8.6) Double Free vulnerability in cisco cisco secure firewall threat defense (ftd) software. EPSS estimates a 0.46% chance of exploitation in the next 30 days, higher than 38.2% of scored vulnerabilities.

Overall risk
34/100
0100
Medium · default modelHow is this calculated?
CVSS score
8.6/10
010
High · v3.1 (CVE.org)
EPSS score
0.46%
0%100%
Low · 0.00 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Timeline

  1. 16-09-2026
    PublishedVulnerability first disclosed.
  2. 17-09-2026
    Last modifiedVulnerability information updated.

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 metrics

2 scores · 2 sources · 1 version

EPSS trend

Probability

0.46%

Chance of exploitation in the next 30 days

Percentile

38%

Versus all other CVEs

30-day change

0.00 pp

From 0.46% on 19-09-2026

19-09-202619-10-2026
EPSS score
0.46%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Cisco1 product
  • 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 | 7.0.2.1 | 7.0.3 | 7.2.0.1 | 7.0.4 | 7.2.1 | 7.0.5 | 7.3.0 | 7.2.2 | 7.2.3 | 7.3.1 | 7.2.4 | 7.0.6 | 7.2.5 | 7.2.4.1 | 7.3.1.1 | 7.4.0 | 7.0.6.1 | 7.2.5.1 | 7.4.1 | 7.2.6 | 7.0.6.2 | 7.4.1.1 | 7.2.7 | 7.2.5.2 | 7.3.1.2 | 7.2.8 | 7.6.0 | 7.4.2 | 7.2.8.1 | 7.0.6.3 | 7.4.2.1 | 7.2.9 | 7.0.7 | 7.7.0 | 7.4.2.2 | 7.2.10 | 7.6.1 | 7.4.2.3 | 7.0.8 | 7.6.2 | 7.7.10 | 7.7.11 | 7.0.8.1 | 7.6.2.1 | 7.7.10.1 | 7.4.2.4 | 7.2.10.2 | 7.4.3 | 7.6.4 | 7.4.4 | 7.0.9 | 7.2.11

1 vendor · 1 product

References

1 links