CVE-2018-1000613 in Legion of the Bouncy Castle
Summary
by MITRE
Legion of the Bouncy Castle Legion of the Bouncy Castle Java Cryptography APIs version prior to version 1.60 contains a CWE-470: Use of Externally-Controlled Input to Select Classes or Code ('Unsafe Reflection') vulnerability in XMSS/XMSS^MT private key deserialization that can result in Deserializing an XMSS/XMSS^MT private key can result in the execution of unexpected code.. This attack appear to be exploitable via A handcrafted private key can include references to unexpected classes which will be picked up from the class path for the executing application.. This vulnerability appears to have been fixed in 1.60 and later.
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Analysis
by VulDB Data Team • 05/12/2025
The vulnerability identified as CVE-2018-1000613 affects the Legion of the Bouncy Castle Java Cryptography APIs, specifically targeting versions prior to 1.60. This represents a critical security flaw that exploits the unsafe use of externally-controlled input in reflection-based code execution mechanisms. The vulnerability resides within the XMSS/XMSS^MT private key deserialization functionality, where the cryptographic library fails to properly validate external inputs during the deserialization process. The affected component operates under CWE-470 classification, which specifically addresses the dangerous practice of allowing external input to influence class or code selection through reflection mechanisms. This weakness creates a pathway for attackers to manipulate the deserialization process by injecting malicious class references that can be resolved from the application's classpath during execution.
The technical exploitation of this vulnerability occurs when a crafted private key contains references to unexpected classes that are subsequently loaded and executed by the Java runtime environment. During the deserialization of XMSS/XMSS^MT private keys, the library's reflection-based mechanisms attempt to instantiate classes based on information contained within the serialized data. When an attacker controls this serialized input, they can specify class names that, when resolved through the classpath, point to malicious code rather than legitimate cryptographic classes. This creates a remote code execution scenario where arbitrary code can be executed with the privileges of the running application. The attack vector is particularly concerning because it requires only a specially crafted private key to be processed by the vulnerable library, making it accessible through various legitimate cryptographic operations that involve key deserialization.
The operational impact of this vulnerability extends beyond simple code execution to encompass potential system compromise and data breach scenarios. An attacker who can influence the deserialization of XMSS/XMSS^MT private keys could gain complete control over systems running vulnerable versions of the Bouncy Castle library. This vulnerability aligns with ATT&CK technique T1059.007 for remote code execution through reflection and T1555.003 for credential access through cryptographic libraries. The attack surface is particularly broad since XMSS/XMSS^MT algorithms are used in post-quantum cryptography implementations, and many applications that process cryptographic keys may inadvertently trigger this vulnerability. The exploitation can occur silently in the background during normal cryptographic operations, making detection challenging and potentially allowing long-term persistence within affected systems.
Mitigation strategies for CVE-2018-1000613 focus primarily on upgrading to Bouncy Castle version 1.60 or later, which includes proper input validation and sanitization mechanisms for the deserialization process. Organizations should implement comprehensive patch management procedures to ensure all systems utilizing the Bouncy Castle library are updated promptly. Additional protective measures include restricting classpath access for applications that process external cryptographic keys, implementing strict input validation for all serialized data, and monitoring for unusual deserialization activities. Security teams should also consider implementing application whitelisting policies to prevent execution of unauthorized classes during deserialization operations. The vulnerability serves as a reminder of the critical importance of validating external inputs in reflection-based operations and demonstrates how cryptographic libraries can become attack vectors when proper security controls are not implemented in their deserialization mechanisms.