CVE-2008-3655 in Ruby
Summary
by MITRE
Ruby 1.8.5 and earlier, 1.8.6 through 1.8.6-p286, 1.8.7 through 1.8.7-p71, and 1.9 through r18423 does not properly restrict access to critical variables and methods at various safe levels, which allows context-dependent attackers to bypass intended access restrictions via (1) untrace_var, (2) $PROGRAM_NAME, and (3) syslog at safe level 4, and (4) insecure methods at safe levels 1 through 3.
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Analysis
by VulDB Data Team • 02/03/2025
Ruby's safe level mechanism was designed to provide a security model that restricts access to potentially dangerous operations based on the execution context of the code. The vulnerability in CVE-2008-3655 stems from improper implementation of these access controls, particularly at safe levels 1 through 4. This flaw allows attackers to bypass intended security restrictions when executing code at elevated safe levels, creating a significant bypass opportunity for malicious actors who can leverage this weakness to access critical system resources and variables that should normally be restricted.
The technical implementation of this vulnerability involves several specific methods and variables that fail to properly enforce access restrictions. The untrace_var method, which should be restricted at safe levels 4 and below, can be exploited to manipulate variable tracing behavior in ways that circumvent normal security boundaries. Additionally, the $PROGRAM_NAME global variable and syslog functionality are improperly accessible at safe level 4, allowing attackers to gain information about the executing program and potentially manipulate system logging mechanisms. The vulnerability also extends to insecure methods that are accessible at safe levels 1 through 3, where the security model fails to properly enforce restrictions on potentially dangerous operations.
The operational impact of this vulnerability is substantial as it enables context-dependent attackers to escalate privileges and access restricted resources without proper authorization. Attackers can exploit this weakness to bypass Ruby's built-in security protections, potentially allowing them to execute arbitrary code, access sensitive data, or manipulate system behavior. The vulnerability is particularly concerning because it affects multiple versions of Ruby including 1.8.5 and earlier, 1.8.6 through 1.8.6-p286, 1.8.7 through 1.8.7-p71, and 1.9 through r18423, meaning a wide range of applications running these versions are potentially vulnerable. This creates a significant attack surface for systems that rely on Ruby's safe level security model for protection.
Security mitigations for this vulnerability require immediate patching of affected Ruby versions to address the improper access control implementations. Organizations should upgrade to Ruby versions that have fixed this vulnerability, typically Ruby 1.8.7-p72 or later, and Ruby 1.9.0 or later. Additionally, developers should review their code to ensure that safe levels are properly configured and that no code relies on the flawed access control behavior. The vulnerability maps to CWE-284 Access Control Issues, specifically related to insufficient access control at different security levels. From an ATT&CK perspective, this vulnerability could be categorized under T1059 Command and Scripting Interpreter and T1566 Phishing, as attackers might use this weakness to execute malicious code or manipulate system behavior through compromised Ruby applications. System administrators should also implement monitoring for suspicious access patterns and ensure that Ruby applications are not running with unnecessary elevated safe levels that could expose these vulnerabilities to attackers.