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A critical vulnerability identified as CVE-2026-20079 exists in the web interface of Cisco Secure Firewall Management Center (FMC) Software. This flaw allows an unauthenticated, remote attacker to completely bypass the authentication mechanism and execute arbitrary scripts and commands with the highest privileges—root access—on the underlying operating system. The vulnerability is rooted in an improper system process that is created during the device’s boot time. An attacker can exploit this weakness by sending a series of crafted HTTP requests to the affected device’s web interface. Due to the flawed boot-time process, these requests are processed without proper authentication checks, granting the attacker the ability to execute a variety of scripts and commands.
CVE-2026-20079 carries a maximum CVSS base score of 10.0, classifying it as a Critical severity vulnerability. The attack vector is network-based, requires low attack complexity, needs no privileges, and does not require user interaction. The scope is changed, and the impact on confidentiality, integrity, and availability is high. Cisco first disclosed the vulnerability in March 2026, but as of August 2026, the Cisco Product Security Incident Response Team (PSIRT) became aware of active exploitation in the wild. This vulnerability affects Cisco Secure FMC Software and Cisco Security Cloud Control (SCC) Firewall Management. Notably, if the FMC management interface is not exposed to the public internet, the attack surface is significantly reduced. At the time of this advisory, no workarounds are available to mitigate this vulnerability; the only solution is to apply the software updates released by Cisco.
DailyCVE Form:
Platform: Cisco Secure FMC
Version: Prior to patched releases
Vulnerability : Authentication Bypass
Severity: CRITICAL (10.0)
date: September 9, 2026
Prediction: Week of September 14
What Undercode Say:
The following analytics, bash commands, and codes are derived from publicly available information and are for educational purposes only.
Analytics
- Active Exploitation: Cisco Talos is actively tracking the exploitation of CVE-2026-20079.
- Threat Actors: Exploitation has been linked to state-sponsored groups (e.g., UAT-12197, UAT-11823) and ransomware operators (UAT-11988).
- Post-Exploitation Activity: Observed activities include the deployment of web shells, JAR-based command executors, Netcat reverse shells, proxy tooling, and credential exfiltration.
- CISA KEV: CISA has added this vulnerability to its Known Exploited Vulnerabilities (KEV) catalog.
Exploit: (Educational Purposes!)
A successful exploit involves sending crafted HTTP requests to the vulnerable FMC web interface. While the exact exploit chain is complex, the following is a conceptual example of how an attacker might interact with the system.
1. Identify a Vulnerable Target:
nmap -p 443 <target_ip> --script http-
2. Craft a Malicious HTTP Request (Conceptual):
The vulnerability stems from a flawed process at boot time. An attacker might send a request to a specific, unprotected endpoint.
curl -k -X GET "https://<target_ip>/path/to/vulnerable/endpoint?cmd=id"
3. Execute Commands as Root:
A successful bypass would allow the execution of system commands with root privileges.
curl -k -X POST "https://<target_ip>/vulnerable/script" -d "command=whoami" Expected output: root
Protection:
- Immediate Patching: The primary and only mitigation is to apply the software updates provided by Cisco. The fix is included in the latest software releases for Cisco Secure FMC.
- Restrict Access: If immediate patching is not possible, ensure that the FMC management interface is not exposed to the public internet or untrusted networks.
- Monitor Logs: Administrators should monitor `/var/log/messages` for any suspicious activity, specifically looking for entries related to
/var/tmp/license.tmp. A log entry like the following is a strong indicator of potential exploitation:Jul 23 16:16:33 firepower sudo: www : PWD=/ ; USER=root ; COMMAND=/usr/local/sf/bin/package_info.pl /var/tmp/license.tmp --lsm
- Follow CISA Guidance: Federal agencies are required to secure vulnerable systems by September 12, 2026.
Impact:
A successful exploit of CVE-2026-20079 allows an unauthenticated, remote attacker to gain root access to the affected Cisco Secure FMC device. This level of access is total and complete, giving the attacker full control over the device and the network it manages. This can lead to:
– Complete System Compromise: The attacker can read, modify, or delete any file on the system.
– Network Pivot: The compromised FMC can be used as a launchpad to attack other devices on the internal network.
– Data Breach: All firewall policies, configurations, and potentially sensitive data managed by the FMC are exposed.
– Persistence: Attackers can install backdoors, web shells, or malware (such as Cyclops Blink) to maintain long-term access.
– Disruption of Operations: An attacker could alter or delete firewall rules, leading to a denial of service or a complete network outage.
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Sources:
Reported By: www.cve.org
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