A Vulnerability in Barracuda Email Security Gateway Could Allow for Remote Command Injection

A Vulnerability has been discovered in Barracuda Email Security Gateway (ESG) which could allow for remote code injection. Barracuda Email Security Gateway is an email security gateway that manages and filters all inbound and outbound email traffic to protect organizations from email-borne threats and data leaks. Successful exploitation of this vulnerability could allow for unauthenticated remote attackers to execute arbitrary code on the server in the context of the System user. Depending on the privileges associated with the user an attacker could then install programs; view, change, or delete data; or create new accounts with full user rights. Users whose accounts are configured to have fewer user rights on the system could be less impacted than those who operate with administrative user rights.

Barracuda has stated CVE-2023-2868 has been used to impact ESG appliances as early as October 2022. Barracuda has identified a subset of appliances where CVE-2023-2868 was utilized to obtain unauthorized access, deploy backdoors, and deploy malware. Barracuda notified affected customers via the ESG user interface of actions to take and reached out to those specific customers. Finally, Barracuda deployed two patches to remediate the vulnerability which were applied to all ESG appliances worldwide.

A Vulnerability has been discovered in Barracuda Email Security Gateway (ESG) which could allow for remote code injection. Details of this vulnerability are as follows:
Tactic: Execution (TA0041):
Technique: Command and Scripting Interpreter (T1059):

• The vulnerability stemmed from incomplete input validation of user supplied .tar files as it pertains to the names of the files contained within the archive. Consequently, a remote attacker could format file names in a particular manner that would result in remotely executing a system command through Perl's qx operator with the privileges of the Email Security Gateway product. (CVE-2023-2868)
  Successful exploitation of this vulnerability could allow for unauthenticated remote attackers to execute arbitrary code on the server in the context of the System user. Depending on the privileges associated with the user an attacker could then install programs; view, change, or delete data; or create new accounts with full user rights. Users whose accounts are configured to have fewer user rights on the system could be less impacted than those who operate with administrative user rights.

We recommend the following actions be taken:

• Ensure your ESG appliance is receiving and applying updates, definitions, and security patches from Barracuda. Contact Barracuda support ([email protected]) to validate if the appliance is up to date. (M1051: Update Software)

• 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 7.6: Perform Automated Vulnerability Scans of Externally-Exposed Enterprise Assets: Perform automated vulnerability scans of externally-exposed enterprise assets using a SCAP-compliant vulnerability scanning tool. Perform scans on a monthly, or more frequent, basis.

• 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.

• 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.

• Safeguard 5.5: Establish and Maintain an Inventory of Service Accounts: Establish and maintain an inventory of service accounts. The inventory, at a minimum, must contain department owner, review date, and purpose. Perform service account reviews to validate that all active accounts are authorized, on a recurring schedule at a minimum quarterly, or more frequently.

• Safeguard 6.8: Define and Maintain Role-Based Access Control: Define and maintain role-based access control, through determining and documenting the access rights necessary for each role within the enterprise to successfully carry out its assigned duties. Perform access control reviews of enterprise assets to validate that all privileges are authorized, on a recurring schedule at a minimum annually, or more frequently.

• Restrict use of certain websites, block downloads/attachments, block Javascript, restrict browser extensions, etc. (M1021: Restrict Web-Based Content)

• Safeguard 9.2: Use DNS Filtering Services: Use DNS filtering services on all enterprise assets to block access to known malicious domains.

• Safeguard 9.3: Maintain and Enforce Network-Based URL Filters: Enforce and update network-based URL filters to limit an enterprise asset from connecting to potentially malicious or unapproved websites. Example implementations include category-based filtering, reputation-based filtering, or through the use of block lists. Enforce filters for all enterprise assets.

• Safeguard 9.6: Block Unnecessary File Types: Block unnecessary file types attempting to enter the enterprise’s email gateway.

• Block execution of code on a system through application control, and/or script blocking. (M1038 : Execution Prevention)

• 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.

• 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.

• Enforce binary and application integrity with digital signature verification to prevent untrusted code from executing. (Mitigation M1045 : Code Signing)

• 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.

• Use signatures or heuristics to detect malicious software. (Mitigation M1049 : Antivirus/Antimalware)

• Safeguard 9.7 : Deploy and Maintain Email Server Anti-Malware Protections: Deploy and maintain email server anti-malware protections, such as attachment scanning and/or sandboxing.

• Safeguard 10.1 : Deploy and Maintain Anti-Malware Software: Deploy and maintain anti-malware software on all enterprise assets.

• Safeguard 10.2 : Configure Automatic Anti-Malware Signature Updates: Configure automatic updates for anti-malware signature files on all enterprise assets.

• Safeguard 10.7 : Use Behavior-Based Anti-Malware Software: Use behavior-based anti-malware software.

• Safeguard 13.2 : Deploy a Host-Based Intrusion Detection Solution: Deploy a host-based intrusion detection solution on enterprise assets, where appropriate and/or supported.

• Safeguard 13.7 : Deploy a Host-Based Intrusion Prevention Solution: Deploy a host-based intrusion prevention solution on enterprise assets, where appropriate and/or supported. Example implementations include use of an Endpoint Detection and Response (EDR) client or host-based IPS agent.