Cisco Secure Firewall Management Center sftunnel denial of service

Summaryinfo

A vulnerability, which was classified as critical, has been found in Cisco Secure Firewall Management Center and Secure Firewall Threat Defense Software. This vulnerability affects unknown code of the component sftunnel. The manipulation leads to denial of service. This vulnerability is documented as CVE-2026-20295. The attack can be initiated remotely. There is not any exploit available. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability was found in Cisco Secure Firewall Management Center and Secure Firewall Threat Defense Software (affected version unknown) and classified as critical. This issue affects an unknown functionality of the component sftunnel. The manipulation with an unknown input leads to a denial of service vulnerability. Using CWE to declare the problem leads to CWE-404. The product does not release or incorrectly releases a resource before it is made available for re-use. Impacted is availability. The summary by CVE is:

A vulnerability in the sftunnel inter-device communication protocol of Cisco Secure FMC Software and Cisco Secure FTD Software could allow an unauthenticated, remote attacker to exhaust the available memory of an affected device. This vulnerability is due to improper management of memory resources during sftunnel TLS connection setup. An attacker could exploit this vulnerability by sending crafted sftunnel TLS frames to an affected device during the connection setup. A successful exploit could allow the attacker to exhaust the available memory on the affected device, which could result in a DoS condition.

It is possible to read the advisory at sec.cloudapps.cisco.com. The identification of this vulnerability is CVE-2026-20295 since 10/08/2025. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. The technical details are unknown and an exploit is not publicly available. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 09/16/2026). The attack technique deployed by this issue is T1499 according to MITRE ATT&CK.

Upgrading eliminates this vulnerability.

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Productinfo

Type

• Firewall Software

Vendor

• Cisco

Name

• Secure Firewall Management Center
• Secure Firewall Threat Defense Software

License

• commercial

Website

• Vendor: https://www.cisco.com/

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