Summary
CVE-2026-20079 is a critical authentication bypass flaw in Cisco Secure FMC. Attackers can send crafted HTTP requests to bypass authentication and run commands as root. Fixed versions are available, with no workaround.
Urgent Actions Required
- Upgrade: Move to the appropriate fixed FMC release.
- Hot fix: Apply the available Cisco hot fix if immediate upgrading is not possible.
- Check logs: Look for /var/tmp/license.tmp activity in FMC logs.
- Suspected compromise: Contact Cisco TAC for recovery support.
- Reduce exposure: Restrict public internet access to the FMC management interface where possible.
Which Systems Are Vulnerable to CVE-2026-20079?
Technical Overview
- Vulnerability Type: Authentication Bypass Using an Alternate Path or Channel (CWE-288)
- Affected Software/Versions:
- Cisco Secure Firewall Management Center (FMC) Software
- CVSS Vector: v3.1
- Attack Vector: Network
- Attack Complexity: Low
- Privileges Required: None
- User Interaction: None
- Scope: Changed
- Confidentiality Impact: High
- Integrity Impact: High
- Availability Impact: High
- Patch Availability: Yes, available
How Does the CVE-2026-20079 Exploit Work?
The attack typically follows these steps:
What Causes CVE-2026-20079?
Vulnerability Root Cause:
CVE-2026-20079 results from an improper system process created during the boot process of Cisco Secure Firewall Management Center. Crafted HTTP requests can exploit this condition to bypass authentication. This allows an unauthenticated remote attacker to execute scripts and commands with root privileges on the underlying operating system.
How Can You Mitigate CVE-2026-20079?
If immediate patching is delayed or not possible:
- Apply the available Cisco hot fix for the affected FMC software version.
- Limit public internet access to the FMC management interface where possible.
- Check FMC logs for /var/tmp/license.tmp activity to identify possible exploitation.
- If indicators of compromise are found, contact Cisco TAC for recovery assistance.
- Upgrade to the appropriate Cisco hardening release as soon as possible.
Which Assets and Systems Are at Risk?
- Asset Types Affected:
- Cisco Secure Firewall Management Center (FMC) - Vulnerable versions of the FMC Software web interface
- Security Cloud Control Firewall Management - The SaaS-delivered firewall management service was affected, but Cisco has deployed the fix
- Exposure Level:
- FMC management interfaces - The vulnerability can be exploited remotely through the web interface using crafted HTTP requests
- Internet-accessible FMC interfaces - Public internet exposure increases the attack surface. Cisco notes that keeping the management interface off the public internet reduces exposure
Will Patching CVE-2026-20079 Cause Downtime?
Patch application impact: Low. Update to the applicable fixed FMC release. Cisco provides fixed versions for supported release branches. Plan the upgrade during a maintenance window to account for the update process.
How Can You Detect CVE-2026-20079 Exploitation?
Exploitation Signatures:
Look for suspicious HTTP requests targeting the FMC web interface, particularly activity associated with authentication bypass and script execution.
Indicators of Compromise (IOCs/IOAs):
- /var/tmp/license.tmp referenced in package_info.pl activity
- home.jsp web shell
- cmd.jar command executor
- Netcat reverse-shell activity
- Known related IPs: 89.34.96[.]56, 208.123.119[.]215, 104.218.165[.]253, and 91.214.78[.]118
- Cyclops Blink hash: 6f98add5d1a7729192b6ad8491d85c505c64836f7881742d6b93bd8e3d2fe461
Behavioral Indicators:
- Unauthenticated access followed by script or command execution
- Unexpected web shells or JAR files in the FMC Tomcat webroot
- Credential or authentication-data access from unexpected processes
- Reverse-shell activity originating from the FMC device
Alerting Strategy:
- Priority: Critical
- Monitor FMC logs for /var/tmp/license.tmp activity.
- Monitor for the CVE-2026-20079 Snort rules: 66075–66080.
- Investigate suspected exploitation immediately and contact Cisco TAC if compromise is suspected.
Remediation & Response
- Remediation Timeline:
- Immediate: Apply the available Cisco fix or upgrade to the applicable hardening release
- After remediation: Verify the FMC instance is running a fixed release and check for signs of prior exploitation
- Incident Response Considerations:
- Check FMC logs for /var/tmp/license.tmp activity using Cisco's recommended search
- If exploitation is suspected, contact Cisco TAC for recovery assistance
- Investigate for web shells, malicious JAR files, reverse-shell activity, and other indicators associated with observed CVE-2026-20079 exploitation
- Review the supplied IOCs and Snort rules 66075–66080 during investigation
Compliance & Governance Notes
- Audit Trail Requirement:
- Retain relevant FMC logs for investigation, including activity involving /var/tmp/license.tmp
- Record the FMC version and applicable Cisco fix applied during remediation
- Document suspected exploitation and any recovery actions taken with Cisco TAC
See How Deception Supercharges NDR For Earlier Threat Detection
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- Detect threats earlier with high-fidelity alerts
- Expose attacker techniques and lateral movement
- Reduce analyst fatigue with actionable context
- Protect critical assets from stealthy exploitation
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CVSS Breakdown Table
| Metric | Value | Description |
|---|---|---|
| Base Score | 10.0 | Maximum-severity vulnerability with remote exploitation and high impact across all three security objectives |
| Attack Vector | Network | Exploitable remotely through the FMC web interface |
| Attack Complexity | Low | Exploitation does not require special conditions |
| Privileges Required | None | The attacker does not need valid authentication |
| User Interaction | None | Exploitation requires no action from a user |
| Scope | Changed | Successful exploitation can affect resources beyond the vulnerable security authority |
| Confidentiality Impact | High | Root access can allow unauthorized access to sensitive information |
| Integrity Impact | High | Root-level access can enable unauthorized changes to the affected system |
| Availability Impact | High | Root access can enable actions that significantly affect system availability |
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