CVE-2013-1624 in Legion-of-the-bouncy-castle-java-crytography-api
Summary
by MITRE
The TLS implementation in the Bouncy Castle Java library before 1.48 and C# library before 1.8 does not properly consider timing side-channel attacks on a noncompliant MAC check operation during the processing of malformed CBC padding, which allows remote attackers to conduct distinguishing attacks and plaintext-recovery attacks via statistical analysis of timing data for crafted packets, a related issue to CVE-2013-0169.
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Analysis
by VulDB Data Team • 05/12/2025
The vulnerability identified as CVE-2013-1624 represents a critical weakness in the Bouncy Castle cryptographic library implementations across both Java and C# platforms. This flaw resides within the Transport Layer Security protocol handling mechanisms, specifically affecting versions prior to 1.48 for Java and 1.8 for C#. The vulnerability stems from insufficient protection against timing side-channel attacks that exploit the temporal variations in cryptographic operations. When processing malformed Cipher Block Chaining padding, the library exhibits inconsistent execution times that correlate with the validity of Message Authentication Code checks, creating a predictable pattern that adversaries can exploit through statistical analysis of timing data.
The technical implementation flaw manifests in the MAC verification process during CBC padding handling where the library performs a nonconstant-time comparison operation. This timing inconsistency occurs because valid and invalid padding checks execute with different execution durations, creating measurable differences that can be amplified through repeated measurements. The vulnerability specifically impacts the TLS protocol implementation where the library processes encrypted packets containing malformed CBC padding structures. Attackers can leverage this timing information to distinguish between valid and invalid padding, ultimately enabling them to recover plaintext information from encrypted communications without possessing the cryptographic keys. This weakness operates under the well-documented category of timing side-channel attacks that have been extensively studied and classified under CWE-386, which addresses the exposure of sensitive information through side channels.
The operational impact of CVE-2013-1624 extends beyond simple information disclosure, as it enables sophisticated plaintext-recovery attacks that can compromise the confidentiality of TLS-protected communications. Remote attackers can systematically analyze timing variations to reconstruct encrypted data, particularly affecting applications that rely on Bouncy Castle for secure communications including web applications, email systems, and enterprise security infrastructure. The vulnerability is particularly dangerous because it operates silently without generating error messages or alerts, making detection difficult for system administrators. This weakness creates a persistent threat vector that can be exploited against any application using vulnerable versions of the Bouncy Castle library, potentially compromising sensitive data such as user credentials, personal information, and business-critical communications.
Mitigation strategies for CVE-2013-1624 require immediate upgrades to patched versions of the Bouncy Castle libraries, specifically version 1.48 for Java and 1.8 for C#. Organizations should conduct comprehensive inventory assessments to identify all systems utilizing vulnerable library versions and implement patch management procedures to ensure timely deployment of security updates. Additional protective measures include implementing constant-time comparison algorithms in cryptographic implementations, utilizing hardware security modules for sensitive operations, and deploying network monitoring tools capable of detecting anomalous timing patterns. The remediation process should also incorporate security testing procedures that validate the absence of timing side-channel vulnerabilities in cryptographic implementations. Organizations may also consider implementing additional layers of security such as intrusion detection systems and protocol-level controls to detect and prevent exploitation attempts, while following established security frameworks and guidelines from organizations such as NIST and ISO standards for cryptographic security practices.