# CVE-2026-20295: Cisco Secure FMC and FTD memory exhaustion in sftunnel

Source: https://junglewise.ai/threats/cve-2026-20295-cisco-secure-fmc-and-ftd-memory-exhaustion-in-sftunnel  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-16. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-20295 · Severity: high · CVSS 8.6 · Published 2026-09-16

Cisco Secure Firewall Management Center (FMC) and Firewall Threat Defense (FTD) products contain a vulnerability in their inter-device communication protocol that allows remote attackers to crash affected devices by exhausting available memory. By sending specially crafted TLS connection frames, an unauthenticated attacker can trigger a denial-of-service condition that renders the security appliance unavailable.

Technologies: [Cisco Secure Firewall Threat Defense](https://junglewise.ai/threats/technologies/firepower-threat-defense), [Cisco Secure Firewall Management Center](https://junglewise.ai/threats/technologies/secure-firewall-management-center). Vendors: [Cisco](https://junglewise.ai/threats/vendors/cisco).

## Quick answers

**Is CVE-2026-20295 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-20295 being exploited in the wild.

**How severe is CVE-2026-20295?** High severity, with a CVSS score of 8.6, published 16 September 2026.

**Which products and versions are affected?** Cisco Secure Firewall Threat Defense <UNKNOWN>; Cisco Secure Firewall Management Center <UNKNOWN>.

**Is there a fix for CVE-2026-20295?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-20295 attacked?** It is attacked over the network, in a network appliance.

**Am I affected by CVE-2026-20295?** Check whether you run Cisco Secure Firewall Threat Defense or Cisco Secure Firewall Management Center at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

This vulnerability exists in the sftunnel inter-device communication protocol and results from improper memory resource management during TLS connection setup. An unauthenticated, remote attacker can exploit this by sending crafted sftunnel TLS frames to an affected device during the connection initialization phase. The vulnerability does not require authentication or user interaction; successful exploitation exhausts available memory on the target device, causing a denial-of-service condition. Cisco has released software updates to address this vulnerability, and no workarounds are available.

## Affected products

- Cisco Secure Firewall Management Center <UNKNOWN>
- Cisco Secure Firewall Threat Defense <UNKNOWN>

## Timeline

- 2026-09-16: disclosed

## References

- [https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-fmcftd-sftun-multivulns-WGVHOrN3](https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-fmcftd-sftun-multivulns-WGVHOrN3)

## Related threats

- [Cisco Snort 3 memory management denial of service](https://junglewise.ai/threats/cve-2026-76489-multiple-cisco-products-are-affected-by-a-vulnerability-in-the)
- [Cisco Snort 3 Detection Engine denial of service in GTP codec](https://junglewise.ai/threats/cve-2026-76445-multiple-cisco-products-are-affected-by-a-vulnerability-in-the)
- [Cisco Snort 3 uncontrolled resource consumption](https://junglewise.ai/threats/cve-2026-20356-as-part-of-cisco-s-ongoing-commitment-to-proactive-security-and)
- [Cisco Snort 3 improper privilege management](https://junglewise.ai/threats/cve-2026-20291-as-part-of-cisco-s-ongoing-commitment-to-proactive-security-and)
- [Cisco Snort 3 incorrect calculation vulnerability](https://junglewise.ai/threats/cve-2026-20236-as-part-of-cisco-s-ongoing-commitment-to-proactive-security-and)