What is CVE-2026-20079?
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.
The record classifies CVE-2026-20079 under weakness class CWE-288. Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs no prior authentication, needs no user interaction, and has high impact on confidentiality, integrity, availability. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 215 days ago.
Severity and exploitation probability
- CVSS v3.1 base score
- 10 — CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H - EPSS (FIRST)
- 88.1% probability of exploitation in the next 30 days, higher than 99.7% of all scored CVEs
- CISA KEV
- Listed since 2026-09-09, federal remediation deadline 2026-09-12
- Threadlinqs priority
- 9/10 — CISA KEV-listed, which Threadlinqs floors at 9
- Published
- 2026-03-04, last modified 2026-09-16
Is CVE-2026-20079 being exploited?
CISA added CVE-2026-20079 to the Known Exploited Vulnerabilities catalog on 2026-09-09, which means the agency holds evidence of exploitation in the wild; US federal civilian agencies had to remediate it by 2026-09-12 under BOD 22-01. Weaponised exploit code for CVE-2026-20079 is publicly available. 4 public proof-of-concept repositories are tracked for this identifier. A ProjectDiscovery Nuclei detection template exists (http/cves/2026/CVE-2026-20079.yaml). It currently carries a trending score of 45 in the Threadlinqs vulnerability feed.
- CyberAuth/CVE-2026-20079 (github)
- 0xBlackash/CVE-2026-20079 (github)
- DiegoArias008/CVE-2026-20079-checker (github)
- trickest/cve (trickest)
Affected products and versions
- Cisco: Secure Firewall Management Center (FMC)
How to fix CVE-2026-20079
Vendor advisory: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-onprem-fmc-authbypass-5JPp45V2. Because CVE-2026-20079 is KEV-listed, US federal civilian agencies were required to apply the vendor fix, or stop using the product, by 2026-09-12. Apply the vendor fix referenced above to every affected product listed in this record, then confirm the running version against the vendor advisory.
Threat activity tracking CVE-2026-20079
2 tracked threats in the Threadlinqs corpus reference CVE-2026-20079, either in the campaign’s CVE list or as an indicator on the campaign record.
- Eclypsium InfraTrust Report: Mass Active Exploitation of Network Management Systems (Cisco FMC/ISE CVE-2026-20079, CVE-2026-76460; SonicWall SMA 1000 CVE-2026-83548/83549; Linux Kernel CopyFail CVE-2026-31431) — CRITICAL · 2026-09-23
- CVE-2026-20316: Cisco Secure Firewall Management Center Hard-coded Password Vulnerability Added to CISA KEV — CRITICAL · 2026-07-29
Sources
Enriched from CVE.org, NVD, FIRST EPSS, CISA KEV, GitHub Security Advisories, public proof-of-concept repositories, ProjectDiscovery Nuclei. Last verified by Threadlinqs on . This product uses the NVD API but is not endorsed or certified by the NVD.