A vulnerability has been discovered in vBulletin which could allow for remote command execution. vBulletin is a tool used to manage and create online forums. Successful exploitation of this vulnerability could allow for remote command execution in the context of the affected service account. Depending on the privileges associated with the service account an attacker could then install programs; view, change, or delete data; or create new accounts with full user rights. Service accounts that are configured to have fewer user rights on the system could be less impacted than those who operate with administrative user rights

THREAT INTELLIGENCE:
There are currently no reports of this vulnerability being exploited in the wild.

SYSTEMS AFFECTED:

• vBulletin versions prior to 5.6.9 PL1
• vBulletin versions prior to 5.6.8 PL1
• vBulletin versions prior to 5.6.7 PL1

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 vBulletin that could allow for remote command execution. A deserialization vulnerability exists in vBulletin that can be triggered pre-authentication via a user registration API. An unauthenticated attacker can send a malicious HTTP request to the application that contains exploit code within the searchprefs parameter. The exploit code is then deserialized and executes commands of the attackers choosing on the underlying operating system as the affected service account.

Tactic: Initial Access (TA0001):

Technique: Exploit Public-Facing Application (T1190):

• vBulletin Deserialization Remote Command Execution Vulnerability (CVE-2023-25135)

Successful exploitation of this vulnerability could allow for remote command execution in the context of the affected service account. Depending on the privileges associated with the service account, an attacker could then install programs; view, change, or delete data; or create new accounts with full user rights. Service accounts that are configured to have fewer user rights on the system could be less impacted than those who operate with administrative user rights.

RECOMMENDATIONS:
We recommend the following actions be taken:

1. Apply appropriate updates provided by vBulletin 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 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.

4. 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:

vBulletin:
https://forum.vbulletin.com/forum/vbulletin-announcements/vbulletin-announcements_aa/4473890-vbulletin-5-6-9-security-patch

Ambionics:
https://www.ambionics.io/blog/vbulletin-unserializable-but-unreachable

CVE:
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-25135

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