A Vulnerability in Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software Could Allow for Unauthorized Access 

 

ITS ADVISORY NUMBER: 
2023-101 

DATE(S) ISSUED: 
09/27/2023 

SUBJECT: 
A Vulnerability in Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software Could Allow for Unauthorized Access 

OVERVIEW: 
A vulnerability has been discovered in Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) software that could allow for unauthorized access. Cisco Adaptive Security Appliance (ASA) Software is the core operating system for the Cisco ASA Family. It delivers enterprise-class firewall capabilities for ASA devices in an array of form factors for any distributed network environment. Cisco Firepower Threat Defense (FTD) Software is an integrative software image combining CISCO ASA and Firepower feature into one hardware and software inclusive system to assist in flagging specific network traffic patterns, create alerts and better control your network. An attacker could exploit this vulnerability by specifying a default connection profile/tunnel group while conducting a brute force attack or while establishing a clientless SSL VPN session using valid credentials. Utilizing the brute force attack to obtain valid credentials, an attacker could use this to establish unauthorized VPN sessions and then install ransomware. 

THREAT INTELLIGENCE: 
In August, Cisco became aware of attempted exploitation of this vulnerability in the wild to gain access to exposed Cisco ASA devices and install ransomware. 

SYSTEMS AFFECTED: 

   

RISK: 
Government: 

  • Large and medium government entities: High 

  • Small government entities: Medium 

   

Businesses: 

  • Large and medium business entities: High 

  • Small business entities: Medium 

Home users: Low 

TECHNICAL SUMMARY: 
A vulnerability has been discovered in Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) software that could allow for unauthorized access. Details of this vulnerability are as follows 

Tactic: Initial Access (TA0001): 

Technique: External Remote Services (T1133): 

  • Cisco Adaptive Security Appliance Software and Firepower Threat Defense Software Remote Access VPN Unauthorized Access Vulnerability​​​​ 

Successful exploitation of this vulnerability could allow for the obtaining of valid credentials An attacker could use this to establish unauthorized VPN sessions and then install ransomware. 

RECOMMENDATIONS: 
We recommend the following actions be taken: 

  • Safeguard 7.1: Establish and Maintain a Vulnerability Management Process: Establish and maintain a documented vulnerability management process for enterprise assets. Review and update documentation annually, or when significant enterprise changes occur that could impact this Safeguard. 

  • Safeguard 7.2: Establish and Maintain a Remediation Process: Establish and maintain a risk-based remediation strategy documented in a remediation process, with monthly, or more frequent, reviews. 

  • Safeguard 7.3: Perform Automated Operating System Patch Management: Perform operating system updates on enterprise assets through automated patch management on a monthly, or more frequent, basis 

  • Safeguard 7.4: Perform Automated Application Patch Management: Perform application updates on enterprise assets through automated patch management on a monthly, or more frequent, basis. 

  • Safeguard 7.5: Perform Automated Vulnerability Scans of Internal Enterprise Assets: Perform automated vulnerability scans of internal enterprise assets on a quarterly, or more frequent, basis. Conduct both authenticated and unauthenticated scans, using a SCAP-compliant vulnerability scanning tool. 

  • Safeguard 7.7: Remediate Detected Vulnerabilities: Remediate detected vulnerabilities in software through processes and tooling on a monthly, or more frequent, basis, based on the remediation process. 

  • Safeguard 12.1: Ensure Network Infrastructure is Up-to-Date: Ensure network infrastructure is kept up-to-date. Example implementations include running the latest stable release of software and/or using currently supported network-as-a-service (NaaS) offerings. Review software versions monthly, or more frequently, to verify software support. 

  • Safeguard 18.1: Establish and Maintain a Penetration Testing Program: Establish and maintain a penetration testing program appropriate to the size, complexity, and maturity of the enterprise. Penetration testing program characteristics include scope, such as network, web application, Application Programming Interface (API), hosted services, and physical premise controls; frequency; limitations, such as acceptable hours, and excluded attack types; point of contact information; remediation, such as how findings will be routed internally; and retrospective requirements. 

  • Safeguard 18.2: Perform Periodic External Penetration Tests: Perform periodic external penetration tests based on program requirements, no less than annually. External penetration testing must include enterprise and environmental reconnaissance to detect exploitable information. Penetration testing requires specialized skills and experience and must be conducted through a qualified party. The testing may be clear box or opaque box. 

  • Safeguard 18.3: Remediate Penetration Test Findings: Remediate penetration test findings based on the enterprise’s policy for remediation scope and prioritization. 

  • Architect sections of the network to isolate critical systems, functions, or resources. Use physical and logical segmentation to prevent access to potentially sensitive systems and information. Use a DMZ to contain any internet-facing services that should not be exposed from the internal network. Configure separate virtual private cloud (VPC) instances to isolate critical cloud systems. (M1030: Network Segmentation)  

  • Safeguard 12.2: Establish and Maintain a Secure Network Architecture: Establish and maintain a secure network architecture. A secure network architecture must address segmentation, least privilege, and availability, at a minimum. 
      

  • Apply the Principle of Least Privilege to all systems and services. Run all software as a non-privileged user (one without administrative privileges) to diminish the effects of a successful attack. (M1026: Privileged Account Management)  

  • Safeguard 4.7: Manage Default Accounts on Enterprise Assets and Software: Manage default accounts on enterprise assets and software, such as root, administrator, and other pre-configured vendor accounts. Example implementations can include: disabling default accounts or making them unusable. 

  • Safeguard 5.4: Restrict Administrator Privileges to Dedicated Administrator Accounts: Restrict administrator privileges to dedicated administrator accounts on enterprise assets. Conduct general computing activities, such as internet browsing, email, and productivity suite use, from the user’s primary, non-privileged account. 

  • Use two or more pieces of evidence to authenticate to a system; such as username and password in addition to a token from a physical smart card or token generator. (M1032: Multi-factor Authentication)  

  • Safeguard 6.5: Require MFA for Administrative Access: Require MFA for all administrative access accounts, where supported, on all enterprise assets, whether managed on-site or through a third-party provider. 
      

  • Prevent access to file shares, remote access to systems, unnecessary services. Mechanisms to limit access may include use of network concentrators, RDP gateways, etc. (M1035: Limit Access to Resource Over Network) 
      

  • Remove or deny access to unnecessary and potentially vulnerable software to prevent abuse by adversaries. (Mitigation M1042: Disable or Remove Feature or Program)  

  • Safeguard 2.3: Address Unauthorized Software: Ensure that unauthorized software is either removed from use on enterprise assets or receives a documented exception. Review monthly, or more frequently. 

  • Safeguard 2.5: Allowlist Authorized Software: Use technical controls, such as application allowlisting, to ensure that only authorized software can execute or be accessed. Reassessbi-annually, or more frequently. 

  • Safeguard 2.7: Allowlist Authorized Scripts: Use technical controls, such as digital signatures and version control, to ensure that only authorized scripts, such as specific .ps1, .py, etc., files, are allowed to execute. Block unauthorized scripts from executing. Reassessbi-annually, or more frequently. 

  • Safeguard 4.1: Establish and Maintain a Secure Configuration Process: Establish and maintain a secure configuration process for enterprise assets (end-user devices, including portable and mobile, non-computing/IoT devices, and servers) and software (operating systems and applications). Review and update documentation annually, or when significant enterprise changes occur that could impact this Safeguard. 

  • Safeguard 4.8: Uninstall or Disable Unnecessary Services on Enterprise Assets and Software: Uninstall or disable unnecessary services on enterprise assets and software, such as an unused file sharing service, web application module, or service function. 

  • Safeguard 18.3: Remediate Penetration Test Findings: Remediate penetration test findings based on the enterprise’s policy for remediation scope and prioritization. 

  • Safeguard 18.5: Perform Periodic Internal Penetration Tests: Perform periodic internal penetration tests based on program requirements, no less than annually. The testing may be clear box or opaque box. 

REFERENCES: 

Cisco: 
https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-ravpn-auth-8LyfCkeC 
 
CVE: 
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-20269 

TLP:CLEAR 
www.cisa.gov/tlp 
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