CVE-2012-4464 in Ruby
Summary
by MITRE
Ruby 1.9.3 before patchlevel 286 and 2.0 before revision r37068 allows context-dependent attackers to bypass safe-level restrictions and modify untainted strings via the (1) exc_to_s or (2) name_err_to_s API function, which marks the string as tainted, a different vulnerability than CVE-2012-4466. NOTE: this issue might exist because of a CVE-2011-1005 regression.
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Analysis
by VulDB Data Team • 01/02/2022
The vulnerability described in CVE-2012-4464 represents a critical security flaw in Ruby versions 1.9.3 prior to patchlevel 286 and 2.0 before revision r37068 that undermines the language's security model through improper handling of string tainting mechanisms. This issue specifically affects the exc_to_s and name_err_to_s API functions, which are used to convert exception objects to string representations during error handling operations. The flaw allows attackers to bypass the safe-level restrictions that Ruby implements to prevent potentially dangerous operations on tainted data, creating a pathway for privilege escalation and code execution within applications that rely on Ruby's security boundaries.
The technical implementation of this vulnerability stems from the improper marking of strings as tainted during exception conversion operations. When Ruby's exception handling mechanisms process errors through exc_to_s or name_err_to_s functions, these operations inadvertently mark the resulting strings as tainted even when they should remain untainted. This behavior violates Ruby's fundamental security principle that untainted strings should remain untainted during normal processing operations. The vulnerability creates a regression from the fix implemented for CVE-2011-1005, which was intended to address similar tainting issues but introduced this new bypass mechanism in the process. This regression demonstrates the complexity of maintaining security boundaries in interpreted languages where exception handling can inadvertently compromise security models.
From an operational impact perspective, this vulnerability enables context-dependent attackers to execute malicious code that would normally be blocked by Ruby's safe-level restrictions. Attackers can exploit this flaw to manipulate untainted strings that should remain protected, potentially allowing them to bypass input validation, modify critical application state, or access restricted system resources. The vulnerability is particularly dangerous in web applications and server-side scripting environments where Ruby handles untrusted input and performs complex exception handling operations. The impact extends beyond simple code execution to potentially enable privilege escalation attacks, as the tainted string manipulation can be leveraged to bypass security checks that would normally prevent dangerous operations.
Security professionals should consider this vulnerability in the context of the Common Weakness Enumeration framework, where it aligns with CWE-20: Improper Input Validation and CWE-377: Insecure Temporary File Creation. The vulnerability also maps to ATT&CK techniques related to privilege escalation and code injection, particularly T1068: Exploitation for Privilege Escalation and T1059: Command and Scripting Interpreter. Organizations should implement immediate mitigations including upgrading to patched versions of Ruby 1.9.3 (patchlevel 286 or later) and Ruby 2.0 (revision r37068 or later), implementing proper input validation measures, and monitoring for unusual string manipulation patterns in error handling code. Additional defensive measures include reviewing application code for potential exploitation vectors in exception handling routines and implementing runtime protections that monitor for unauthorized string tainting operations. The vulnerability underscores the importance of careful regression testing when implementing security fixes and highlights the need for comprehensive security reviews of core language functions that handle error conditions and data conversion operations.