# CVE-2026-20295: Denial of service in Cisco Secure Firewall Management Center (FMC)

> Unauthenticated remote attackers can cause denial of service by exhausting memory via crafted sftunnel TLS frames in Cisco Secure Firewall Management Center and Threat Defense.

- **Severity:** High 8.6 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 16 Sep 2026
- **Updated:** 17 Sep 2026
- **Also known as:** GHSA-2x4m-98h8-xp8g

## What is CVE-2026-20295?

CVE-2026-20295 is a high-severity denial of service vulnerability in Cisco Secure Firewall Management Center (FMC), published on 16 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

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.

Weakness: CWE-789 (Memory Allocation with Excessive Size Value)

## Which versions are affected by CVE-2026-20295?


## How do I fix CVE-2026-20295?

No fix has been published for CVE-2026-20295 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-20295 being exploited?

There is no known exploitation of CVE-2026-20295 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-20295 and fix it if it is affected.

What it is: CVE-2026-20295 is a high-severity denial of service vulnerability in Cisco Secure Firewall Management Center (FMC), published on 16 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-20295 in the wild and no public exploit code.

Affected product: Cisco Secure Firewall Management Center (FMC). No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-20295/ (Markdown: https://insights.sbomify.com/CVE-2026-20295/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-20295
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-20295
- OSV: https://osv.dev/vulnerability/CVE-2026-20295

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-20295/
Summaries are generated and may contain mistakes; the official description above is the record.