CVE-2026-20079
Cisco Secure Firewall Management Center (FMC) · Firewalls, VPNs and remote access
Cisco Firewall Management Center Authentication Bypass Using an Alternate Path or Channel Vulnerability
At a glance
Exploited. Added to CISA’s catalog of exploited vulnerabilities on September 9, 2026.
CISA asks you to hunt for signs of compromise: patching is not enough if the device has already been breached.
Affected product: Cisco Secure Firewall Management Center (FMC) (category Firewalls, VPNs and remote access, indicative classification). Name in CISA’s catalog: Cisco Secure Firewall Management Center (FMC) and Security Cloud Control (SCC) Firewall Management.
What should I do?
Apply the patches or mitigations from Cisco; if none are available, stop using the product. Start with internet-facing devices.
CISA also asks you to hunt for signs of compromise: patching is not enough if the device has already been breached.
Deadline set by CISA for US federal agencies: 3 days (due September 12, 2026). It only binds those agencies, but it is a useful measure of urgency.
- Cisco security advisories page (general page, not the advisory for this vulnerability)
- The vendor’s specific advisory is listed in the NVD references: CVE-2026-20079 on the NVD website.
Original text of the required action (CISA)
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.
Timeline
- Vulnerability published Publication date (NVD)
- Exploitation confirmed Added to CISA’s KEV catalog
- CISA deadline Remediation deadline set for US federal agencies
The facts, with their sources
- Exploitation confirmed
- Yes, on September 9, 2026 Date added to the catalog of exploited vulnerabilities. Exploitation itself may have started earlier. Source: KEV catalog, collected September 29, 2026 at 14:57 UTC
- Ransomware
- No known use to date That does not guarantee it is not being used: the information is not public. Source: KEV catalog, collected September 29, 2026 at 14:57 UTC
- Hunt for compromise
- Requested by CISA Source: KEV catalog, collected September 29, 2026 at 14:57 UTC
- CISA required action
- Apply the patches or mitigations from Cisco; if none are available, stop using the product. Start with internet-facing devices. Rewritten by this site from CISA’s original text. Source: KEV catalog, collected September 29, 2026 at 14:57 UTC
- CISA deadline
- September 12, 2026, 3 days Set for US federal agencies: a measure of urgency, not an obligation elsewhere. Source: KEV catalog, collected September 29, 2026 at 14:57 UTC
- Vulnerability published
- March 4, 2026 Source: National Vulnerability Database (NVD), collected September 29, 2026 at 15:00 UTC
- Product according to CISA
- Cisco Secure Firewall Management Center (FMC) and Security Cloud Control (SCC) Firewall Management Filed by this site under “Firewalls, VPNs and remote access” (indicative classification). Source: KEV catalog, collected September 29, 2026 at 14:57 UTC
- CVSS vector
- CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H Technical detail of the score: attack vector, complexity, impact. Source: National Vulnerability Database (NVD), collected September 29, 2026 at 15:00 UTC
Severity and activity
Score from the vendor or CISA, relayed by the NVD. Collected Sep 29, 2026.
FIRST’s EPSS model. Since exploitation is already confirmed, this figure is mostly useful to compare activity. Collected Sep 29, 2026.
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.
Official description from the NVD, collected Sep 29, 2026. CVE® description © The MITRE Corporation.
Cisco Secure Firewall Management Center (FMC) Software and Cisco Security Cloud Control (SCC) Firewall Management contain an authentication Bypass using an alternate path or channel vulnerability that 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.
Summary from CISA (KEV catalog).
CERT-FR advisories
No advisory among the latest CERT-FR publications this site follows. That does not mean there are none.
Information reused under the Open Licence 2.0 (Etalab); the date of last update is shown for each advisory. This site is neither affiliated with nor endorsed by ANSSI.
Sources for this page
- CISA KEV catalog: exploitation, date added, required action, deadline, ransomware.
- NVD (NIST): CVSS severity, publication date, description, vendor references.
- EPSS (FIRST): probability of exploitation.
- CERT-FR: advisories and alerts (in French).
- Brand and category: indicative classification by this site (method).