CVE-2013-5915 in PolarSSL
Summary
by MITRE
The RSA-CRT implementation in PolarSSL before 1.2.9 does not properly perform Montgomery multiplication, which might allow remote attackers to conduct a timing side-channel attack and retrieve RSA private keys.
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Analysis
by VulDB Data Team • 01/08/2022
The vulnerability identified as CVE-2013-5915 affects the PolarSSL cryptographic library version 1.2.8 and earlier, specifically targeting the RSA-CRT (Chinese Remainder Theorem) implementation. This flaw represents a critical security weakness that undermines the fundamental security assumptions of RSA key operations. The issue stems from improper implementation of Montgomery multiplication, a mathematical operation crucial for efficient modular arithmetic in RSA cryptography. When cryptographic libraries fail to properly implement such core mathematical functions, they create exploitable side-channel vulnerabilities that can compromise entire security infrastructures.
The technical flaw manifests in the timing side-channel attack vector where attackers can observe and analyze the time variations in cryptographic operations to infer information about the private key. In RSA-CRT implementations, the Montgomery multiplication process should execute in constant time to prevent such leakage, but PolarSSL's implementation fails to achieve this property. This vulnerability directly maps to CWE-310, which categorizes weaknesses related to cryptographic implementation flaws and side-channel attacks. The timing variations occur because the Montgomery multiplication algorithm does not maintain consistent execution time regardless of the input values, creating observable patterns that can be exploited through statistical analysis.
The operational impact of this vulnerability is severe and far-reaching across any system utilizing PolarSSL versions prior to 1.2.9 for RSA key operations. Attackers can potentially recover RSA private keys through repeated timing measurements, which would compromise the confidentiality and integrity of all encrypted communications protected by those keys. This vulnerability affects web servers, secure communication protocols, digital signature systems, and any application relying on RSA-CRT for private key operations. The attack requires only network access to observe timing variations, making it particularly dangerous as it can be conducted remotely without physical access to the target system. Organizations using vulnerable versions of PolarSSL face significant risk of data breaches, man-in-the-middle attacks, and credential compromise that could affect thousands of users and systems.
Mitigation strategies for CVE-2013-5915 require immediate action to upgrade to PolarSSL version 1.2.9 or later, where the Montgomery multiplication implementation has been corrected to prevent timing side-channel attacks. System administrators should also consider implementing additional security controls such as constant-time cryptographic implementations, randomizing operation timing, and monitoring for unusual network behavior that might indicate exploitation attempts. The vulnerability demonstrates the critical importance of proper cryptographic implementation practices and adherence to established security standards. Organizations should conduct comprehensive audits of their cryptographic libraries and dependencies to identify similar vulnerabilities, as this flaw represents a common category of issues that can be systematically addressed through proper security testing and code review processes aligned with industry best practices.