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

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-20135
StatePUBLISHED
Assignercisco
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-16 21:17:07 UTC
Updated2026-09-18 13:28:28 UTC
DescriptionA 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.

Risk And Classification

Primary CVSS: v3.1 8.6 HIGH from [email protected]

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

EPSS: 0.004570000 probability, percentile 0.389510000 (date 2026-09-20)

Problem Types: CWE-415 | CWE-415 Double Free

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary8.6HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
3.1CNACVSSV3_18.6HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Changed
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Cisco Cisco Secure Firewall Threat Defense FTD Software affected 7.0.0 Not specified
CNA Cisco Cisco Secure Firewall Threat Defense FTD Software affected 7.0.0.1 Not specified
CNA Cisco Cisco Secure Firewall Threat Defense FTD Software affected 7.0.1 Not specified
CNA Cisco Cisco Secure Firewall Threat Defense FTD Software affected 7.0.1.1 Not specified
CNA Cisco Cisco Secure Firewall Threat Defense FTD Software affected 7.0.2 Not specified
CNA Cisco Cisco Secure Firewall Threat Defense FTD Software affected 7.2.0 Not specified
CNA Cisco Cisco Secure Firewall Threat Defense FTD Software affected 7.0.2.1 Not specified
CNA Cisco Cisco Secure Firewall Threat Defense FTD Software affected 7.0.3 Not specified
CNA Cisco Cisco Secure Firewall Threat Defense FTD Software affected 7.2.0.1 Not specified
CNA Cisco Cisco Secure Firewall Threat Defense FTD Software affected 7.0.4 Not specified
CNA Cisco Cisco Secure Firewall Threat Defense FTD Software affected 7.2.1 Not specified
CNA Cisco Cisco Secure Firewall Threat Defense FTD Software affected 7.0.5 Not specified
CNA Cisco Cisco Secure Firewall Threat Defense FTD Software affected 7.3.0 Not specified
CNA Cisco Cisco Secure Firewall Threat Defense FTD Software affected 7.2.2 Not specified
CNA Cisco Cisco Secure Firewall Threat Defense FTD Software affected 7.2.3 Not specified
CNA Cisco Cisco Secure Firewall Threat Defense FTD Software affected 7.3.1 Not specified
CNA Cisco Cisco Secure Firewall Threat Defense FTD Software affected 7.2.4 Not specified
CNA Cisco Cisco Secure Firewall Threat Defense FTD Software affected 7.0.6 Not specified
CNA Cisco Cisco Secure Firewall Threat Defense FTD Software affected 7.2.5 Not specified
CNA Cisco Cisco Secure Firewall Threat Defense FTD Software affected 7.2.4.1 Not specified
CNA Cisco Cisco Secure Firewall Threat Defense FTD Software affected 7.3.1.1 Not specified
CNA Cisco Cisco Secure Firewall Threat Defense FTD Software affected 7.4.0 Not specified
CNA Cisco Cisco Secure Firewall Threat Defense FTD Software affected 7.0.6.1 Not specified
CNA Cisco Cisco Secure Firewall Threat Defense FTD Software affected 7.2.5.1 Not specified
CNA Cisco Cisco Secure Firewall Threat Defense FTD Software affected 7.4.1 Not specified
CNA Cisco Cisco Secure Firewall Threat Defense FTD Software affected 7.2.6 Not specified
CNA Cisco Cisco Secure Firewall Threat Defense FTD Software affected 7.0.6.2 Not specified
CNA Cisco Cisco Secure Firewall Threat Defense FTD Software affected 7.4.1.1 Not specified
CNA Cisco Cisco Secure Firewall Threat Defense FTD Software affected 7.2.7 Not specified
CNA Cisco Cisco Secure Firewall Threat Defense FTD Software affected 7.2.5.2 Not specified
CNA Cisco Cisco Secure Firewall Threat Defense FTD Software affected 7.3.1.2 Not specified
CNA Cisco Cisco Secure Firewall Threat Defense FTD Software affected 7.2.8 Not specified
CNA Cisco Cisco Secure Firewall Threat Defense FTD Software affected 7.6.0 Not specified
CNA Cisco Cisco Secure Firewall Threat Defense FTD Software affected 7.4.2 Not specified
CNA Cisco Cisco Secure Firewall Threat Defense FTD Software affected 7.2.8.1 Not specified
CNA Cisco Cisco Secure Firewall Threat Defense FTD Software affected 7.0.6.3 Not specified
CNA Cisco Cisco Secure Firewall Threat Defense FTD Software affected 7.4.2.1 Not specified
CNA Cisco Cisco Secure Firewall Threat Defense FTD Software affected 7.2.9 Not specified
CNA Cisco Cisco Secure Firewall Threat Defense FTD Software affected 7.0.7 Not specified
CNA Cisco Cisco Secure Firewall Threat Defense FTD Software affected 7.7.0 Not specified
CNA Cisco Cisco Secure Firewall Threat Defense FTD Software affected 7.4.2.2 Not specified
CNA Cisco Cisco Secure Firewall Threat Defense FTD Software affected 7.2.10 Not specified
CNA Cisco Cisco Secure Firewall Threat Defense FTD Software affected 7.6.1 Not specified
CNA Cisco Cisco Secure Firewall Threat Defense FTD Software affected 7.4.2.3 Not specified
CNA Cisco Cisco Secure Firewall Threat Defense FTD Software affected 7.0.8 Not specified
CNA Cisco Cisco Secure Firewall Threat Defense FTD Software affected 7.6.2 Not specified
CNA Cisco Cisco Secure Firewall Threat Defense FTD Software affected 7.7.10 Not specified
CNA Cisco Cisco Secure Firewall Threat Defense FTD Software affected 7.7.11 Not specified
CNA Cisco Cisco Secure Firewall Threat Defense FTD Software affected 7.0.8.1 Not specified
CNA Cisco Cisco Secure Firewall Threat Defense FTD Software affected 7.6.2.1 Not specified
CNA Cisco Cisco Secure Firewall Threat Defense FTD Software affected 7.7.10.1 Not specified
CNA Cisco Cisco Secure Firewall Threat Defense FTD Software affected 7.4.2.4 Not specified
CNA Cisco Cisco Secure Firewall Threat Defense FTD Software affected 7.2.10.2 Not specified
CNA Cisco Cisco Secure Firewall Threat Defense FTD Software affected 7.4.3 Not specified
CNA Cisco Cisco Secure Firewall Threat Defense FTD Software affected 7.6.4 Not specified
CNA Cisco Cisco Secure Firewall Threat Defense FTD Software affected 7.4.4 Not specified
CNA Cisco Cisco Secure Firewall Threat Defense FTD Software affected 7.0.9 Not specified
CNA Cisco Cisco Secure Firewall Threat Defense FTD Software affected 7.2.11 Not specified

References

ReferenceSourceLinkTags
sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ftd-tl... [email protected] sec.cloudapps.cisco.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Additional Advisory Data

Exploits

CNA: The Cisco Product Security Incident Response Team (PSIRT) is not aware of any public announcements or malicious use of the vulnerability that is described in this advisory.

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