CVE-2013-1802 in extlib
Summary
by MITRE
The extlib gem 0.9.15 and earlier for Ruby does not properly restrict casts of string values, which might allow remote attackers to conduct object-injection attacks and execute arbitrary code, or cause a denial of service (memory and CPU consumption) by leveraging Action Pack support for (1) YAML type conversion or (2) Symbol type conversion, a similar vulnerability to CVE-2013-0156.
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Analysis
by VulDB Data Team • 02/25/2019
The CVE-2013-1802 vulnerability resides within the extlib gem version 0.9.15 and earlier, representing a critical security flaw that exploits improper type casting mechanisms in Ruby applications. This vulnerability specifically targets the interaction between the extlib gem and Ruby on Rails Action Pack components, creating a pathway for remote attackers to manipulate object serialization processes. The flaw enables malicious actors to inject arbitrary objects into the application's memory space through carefully crafted input that bypasses normal type validation checks. The vulnerability demonstrates characteristics consistent with CWE-707, which addresses improper neutralization of special elements used in object-oriented languages, making it particularly dangerous in web application contexts where user input is processed through serialization frameworks.
The technical implementation of this vulnerability leverages Ruby's YAML and Symbol type conversion capabilities within Action Pack's parameter parsing mechanisms. When the extlib gem processes incoming parameters, it fails to properly validate or restrict the types of values being cast, allowing attackers to inject serialized objects that get deserialized within the application context. This creates an object injection scenario where malicious YAML or Symbol representations can be converted into executable code objects, effectively bypassing standard input sanitization measures. The vulnerability operates at the intersection of serialization frameworks and type coercion systems, similar to the well-known CVE-2013-0156, which also exploited YAML deserialization flaws in Rails applications. The attack vector specifically targets the way Action Pack handles type conversion for parameters, where string inputs are improperly cast to potentially dangerous object types without adequate validation.
The operational impact of CVE-2013-1802 extends beyond simple code execution to include significant resource consumption that can lead to denial of service conditions. Attackers can exploit this vulnerability to consume excessive memory and CPU resources through crafted payloads that cause the application to perform intensive object creation and processing operations. The vulnerability allows for both remote code execution and resource exhaustion attacks, making it particularly dangerous in multi-tenant environments or applications with limited computational resources. When exploited, the vulnerability can cause applications to crash or become unresponsive, effectively rendering services unavailable to legitimate users while simultaneously providing attackers with potential execution capabilities. This dual nature of the vulnerability makes it especially attractive to threat actors seeking both system compromise and service disruption.
Mitigation strategies for CVE-2013-1802 focus on updating the affected extlib gem to versions that properly validate type conversions and restrict unsafe casting operations. Organizations should immediately upgrade to extlib gem versions that address the specific type conversion flaws, typically those released after the vulnerability disclosure. Additionally, implementing input validation at multiple layers of the application stack can help prevent malicious payloads from reaching the vulnerable serialization components. Network-level protections such as web application firewalls and intrusion detection systems can provide additional defense-in-depth measures by monitoring for suspicious parameter patterns associated with known exploitation techniques. The vulnerability highlights the importance of proper object serialization security practices and aligns with ATT&CK technique T1059.007 for command and scripting interpreter execution, as successful exploitation can lead to arbitrary code execution within the application context. Regular security auditing of gem dependencies and maintaining up-to-date security patches remain critical practices for preventing similar vulnerabilities from being exploited in production environments.