CVE-2013-0156 in Ruby on Rails
Summary
by MITRE
active_support/core_ext/hash/conversions.rb in Ruby on Rails before 2.3.15, 3.0.x before 3.0.19, 3.1.x before 3.1.10, and 3.2.x before 3.2.11 does not properly restrict casts of string values, which allows remote attackers to conduct object-injection attacks and execute arbitrary code, or cause a denial of service (memory and CPU consumption) involving nested XML entity references, by leveraging Action Pack support for (1) YAML type conversion or (2) Symbol type conversion.
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Analysis
by VulDB Data Team • 01/31/2025
The vulnerability identified as CVE-2013-0156 represents a critical object injection flaw within the Ruby on Rails framework that affects multiple versions across different release branches. This vulnerability resides in the active_support/core_ext/hash/conversions.rb file and specifically targets the framework's handling of string value casting operations. The flaw enables remote attackers to manipulate the type conversion mechanisms within Action Pack, creating a pathway for executing arbitrary code or inducing denial of service conditions through carefully crafted input. The vulnerability's impact extends across Rails versions 2.3.14 and earlier, 3.0.18 and earlier, 3.1.9 and earlier, and 3.2.10 and earlier, making it a widespread concern for applications utilizing these framework versions.
The technical mechanism behind this vulnerability involves the improper restriction of string value casting within the YAML and Symbol type conversion processes. When Rails processes incoming data through Action Pack's support for these conversion types, it fails to adequately validate or sanitize the input strings before attempting to cast them into objects. This oversight allows attackers to inject malicious payloads that can be interpreted as valid YAML or Symbol representations, leading to object injection attacks. The vulnerability particularly exploits nested XML entity references that can cause excessive memory and CPU consumption during parsing, creating opportunities for both remote code execution and resource exhaustion attacks. This flaw aligns with CWE-94, which describes the weakness of executing arbitrary code through improper input validation, and specifically relates to CWE-400, addressing improper resource exhaustion through XML external entity expansion.
The operational impact of CVE-2013-0156 extends beyond simple code execution to encompass significant system stability risks. Attackers can leverage this vulnerability to perform remote code execution against vulnerable applications, potentially gaining full control over affected systems. The memory and CPU consumption aspects of this vulnerability make it particularly dangerous in environments where resource constraints are critical, as it can be used to perform denial of service attacks that exhaust system resources. Applications processing user input through Rails' parameter parsing mechanisms become immediately vulnerable, especially those that accept XML data from untrusted sources. The attack surface is broad given that Rails is widely used across web applications, making this vulnerability particularly concerning for organizations with multiple Rails-based systems.
Mitigation strategies for CVE-2013-0156 focus primarily on upgrading to patched versions of Ruby on Rails, with specific recommendations to update to Rails 2.3.15, 3.0.19, 3.1.10, or 3.2.11 respectively. Organizations should implement comprehensive patch management procedures to ensure all affected systems receive timely updates. Additionally, implementing input validation and sanitization measures can provide defense-in-depth protection, particularly when upgrading is not immediately feasible. Network-level protections such as web application firewalls can help detect and block malicious payloads attempting to exploit this vulnerability. Security monitoring should include detection of unusual memory consumption patterns and parsing activities that might indicate exploitation attempts. The vulnerability's classification under ATT&CK technique T1059.001 for command and script injection highlights the need for comprehensive security controls that address both the immediate patching requirements and broader application security practices. Organizations should also consider implementing automated vulnerability scanning tools that can identify systems running vulnerable versions of Rails and prioritize remediation efforts accordingly.