A vulnerability has been discovered in Sophos Firewall that could allow for remote code execution. Sophos Firewall is a next generation firewall product which enables users to manage, detect and respond to threats on the network. Successful exploitation of this vulnerability could allow for remote code execution in the context of the affected service account. Depending on the privileges associated with the account, an attacker could then install programs; view, change, or delete data; or create new accounts with full user rights.

THREAT INTELLIGENCE:
Sophos is aware that an exploit for CVE-2022-3236 exists in the wild.

SYSTEMS AFFECTED:

• Sophos Firewall v19.0 MR1 (19.0.1) and older

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:

Tactic: Initial Access (TA0001):

Technique: Exploit Public-Facing Application (T1190):

• A code injection vulnerability in the User Portal and Webadmin of Sophos Firewall (CVE-2022-3236)

Successful exploitation of this vulnerability could allow for remote code execution in the context of the affected service account. Depending on the privileges associated with the account an attacker could then install programs; view, change, or delete data; or create new accounts with full user rights.

RECOMMENDATIONS:

We recommend the following actions be taken:

1. Apply appropriate updates provided by Sophos to vulnerable systems immediately after appropriate testing. (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 7.4: 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.

2. 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.

3. 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.

4. 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)

5. Use intrusion detection signatures to block traffic at network boundaries. (M1031: Network Intrusion Prevention)

• Safeguard 13.3: Deploy a Network Intrusion Detection Solution: Deploy a network intrusion detection solution on enterprise assets, where appropriate. Example implementations include the use of a Network Intrusion Detection System (NIDS) or equivalent cloud service provider (CSP) service.
• Safeguard 13.8: Deploy a Network Intrusion Prevention Solution: Deploy a network intrusion prevention solution, where appropriate. Example implementations include the use of a Network Intrusion Prevention System (NIPS) or equivalent CSP service.

6. Use capabilities to detect and block conditions that may lead to or be indicative of a software exploit occurring. (M1050: Exploit Protection)

• Safeguard 13.10: Performing Application Layer Filtering:  Perform application layer filtering. Example implementations include a filtering proxy, application layer firewall, or gateway.

REFERENCES:

Sophos:
https://www.sophos.com/en-us/security-advisories/sophos-sa-20220923-sfos-rce
https://docs.sophos.com/nsg/sophos-firewall/18.5/Help/en-us/webhelp/onlinehelp/AdministratorHelp/Authentication/OneTimePassword/index.html

CVE:
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2022-3236

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