# CVE-2026-76420: Cisco Secure Firewall Management Center Software Impersonated sftunnel Connection Vulnerability

> An unauthenticated remote attacker can impersonate a peer device to execute commands as root and control FMC APIs if the sftunnel connection is down.

- **Severity:** Critical 9.0 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/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-4fw2-5j8h-69f2

## What is CVE-2026-76420?

CVE-2026-76420 is a critical authentication bypass 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 internal configuration of the Apache JServ Protocol (AJP) connector for Cisco Secure FMC Software could allow an unauthenticated, remote attacker to impersonate a peer device.

This vulnerability is due to incorrect initialization of encryption parameters for the AJP connector at boot time. An attacker could exploit this vulnerability by sending crafted packets to the AJP connector. A successful exploit could allow the attacker to execute commands as root and gain full control over the FMC REST APIs on the affected device.
Note: This vulnerability can be exploited only if the valid sftunnel connection between Cisco Secure FMC Software and Cisco Secure FTD Software is down.

Weakness: CWE-285 (Improper Authorization)

## Which versions are affected by CVE-2026-76420?


## How do I fix CVE-2026-76420?

No fix has been published for CVE-2026-76420 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-76420 being exploited?

There is no known exploitation of CVE-2026-76420 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-76420 and fix it if it is affected.

What it is: CVE-2026-76420 is a critical authentication bypass 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-2026-76420 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-2026-76420/ (Markdown: https://insights.sbomify.com/CVE-2026-76420/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-76420
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-76420
- OSV: https://osv.dev/vulnerability/CVE-2026-76420

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-76420/
Summaries are generated and may contain mistakes; the official description above is the record.