---
title: "CVE-2026-20343: Cisco Secure FMC Software - Authentication Bypass"
description: "Cisco Secure FMC Software contains an information disclosure and denial of service vulnerability caused by lack of authentication in a critical API, letting unauthenticated remote attackers download sensitive files and exhaust disk space, exploit requires no authentication."
url: https://panop.io/threat-heartbeat/CVE-2026-20343/
---

# CVE-2026-20343 Cisco Secure FMC Software - Authentication Bypass

Cisco Secure FMC Software contains an information disclosure and denial of service vulnerability caused by lack of authentication in a critical API, letting unauthenticated remote attackers download sensitive files and exhaust disk space, exploit requires no authentication.

CVSS base score 7.5 /10

High

CISA KEV

Not listed

Public exploit

None known

Authentication

Not required

EPSS

0.45% chance of exploitation in 30 days

[View the NVD record ↗](https://nvd.nist.gov/vuln/detail/CVE-2026-20343)

## Details

Type

Authentication Bypass

Impact

Information Disclosure, Denial Of Service

CVSS vector

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

Published

16 September 2026

Updated

15 October 2026

Weakness

[CWE-306](https://cwe.mitre.org/data/definitions/306.html)

## Vendor fix

Update to the latest version with authentication enforced on the critical API.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

## References

- [https://nvd.nist.gov/vuln/detail/CVE-2026-20343](https://nvd.nist.gov/vuln/detail/CVE-2026-20343)
- [https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-fmc-mulivulns-4PsnFwvx](https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-fmc-mulivulns-4PsnFwvx)

[← All CVEs](https://panop.io/threat-heartbeat/)

## What this record can't tell you

- Whether you run the affected software, and where
- Whether an attacker can actually reach and exploit it
- The misconfigurations that never get a CVE number
- What it would cost the business, ranked into what to fix first

Panop answers these inside your environment, for this CVE and every other finding.

[Book a demo](https://panop.io/demo)