CVE-2026-20079
Cisco Firewall Management Center Authentication Bypass Using an Alternate Path or Channel Vulnerability
Does this matter?
Known to be exploited in the wild (CISA KEV, CISA remediation deadline 12 September 2026). Treat as an emergency change: patch or isolate now, then hunt for prior compromise.
Description
A vulnerability in the web interface of Cisco Secure Firewall Management Center (FMC) Software could allow an unauthenticated, remote attacker to bypass authentication and execute script files on an affected device to obtain root access to the underlying operating system. This vulnerability is due to an improper system process that is created at boot time. An attacker could exploit this vulnerability by sending crafted HTTP requests to an affected device. A successful exploit could allow the attacker to execute a variety of scripts and commands that allow root access to the device.
- CVSS 3.1
- 10.0 CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
- EPSS
- 75.75% probability · 99th percentile
- CISA KEV
- Listed 9 September 2026 · due 12 September 2026
- Weakness
- CWE-288
- Affected
- cisco/secure firewall management center
- Source
- psirt@cisco.com
CISA notes
Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines. https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-onprem-fmc-authbypass-5JPp45V2 ; BOD 26-04: https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk ; Forensics Triage Requirements: https://www.cisa.gov/news-events/directives/bod-26-04-implementation-guidance-prioritizing-security-updates-based-risk ; https://nvd.nist.gov/vuln/detail/CVE-2026-20079
References
- https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-onprem-fmc-authbypass-5JPp45V2Vendor Advisory
- http://seclists.org/fulldisclosure/2026/Aug/80Exploit, Mailing List, Third Party Advisory
- https://blog.talosintelligence.com/fmc-ongoing-exploitation/Exploit, Third Party Advisory
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-20079US Government Resource
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.