CVE-2012-4481 in Ruby
Summary
by MITRE
The safe-level feature in Ruby 1.8.7 allows context-dependent attackers to modify strings via the NameError#to_s method when operating on Ruby objects. NOTE: this issue is due to an incomplete fix for CVE-2011-1005.
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Analysis
by VulDB Data Team • 01/02/2022
The vulnerability described in CVE-2012-4481 represents a significant security flaw in Ruby 1.8.7's safe-level implementation that enables context-dependent attackers to manipulate string objects through the NameError#to_s method. This issue emerged as an incomplete remediation for a previously identified vulnerability, CVE-2011-1005, which demonstrates how security fixes can sometimes introduce new attack vectors when not thoroughly validated. The flaw specifically affects Ruby versions prior to 1.9.3, making it particularly concerning for legacy systems that have not been properly updated.
The technical core of this vulnerability lies in Ruby's safe-level mechanism, which is designed to restrict access to potentially dangerous operations based on the execution context. When a NameError exception occurs, the to_s method can be exploited to modify string objects in ways that bypass normal security restrictions. This occurs because the safe-level feature fails to properly validate or sanitize string modifications when processing exception objects, particularly in contexts where the safe level is set to restrict certain operations. The vulnerability manifests when Ruby processes NameError objects through the to_s method, allowing attackers to inject malicious content into string representations that should remain protected.
The operational impact of CVE-2012-4481 extends beyond simple string manipulation, as it can potentially enable attackers to execute arbitrary code or access restricted system resources. When exploited, this vulnerability allows context-dependent attackers to modify string objects in memory, which can lead to code injection scenarios or privilege escalation within applications that rely on Ruby's safe-level protections. Applications running on affected Ruby versions may become vulnerable to attacks that exploit this flaw, particularly those that process user input through exception handling mechanisms or that depend on string representations of error objects for security decisions.
This vulnerability aligns with CWE-20, which addresses improper input validation, and relates to the ATT&CK technique T1059.007 for command and script injection. The flaw demonstrates how incomplete security patches can create new attack surfaces, as the remediation for CVE-2011-1005 was insufficient to prevent the specific exploitation path identified in CVE-2012-4481. Organizations should prioritize updating to Ruby 1.9.3 or later versions where this vulnerability has been properly addressed, and implement additional monitoring for unusual string modifications in applications that handle exception objects. Security teams should also review their Ruby application code to ensure that exception handling does not inadvertently expose string manipulation vulnerabilities through methods like to_s that could be exploited by attackers.