CVE-2011-4574 in PolarSSL
Summary
by MITRE • 10/27/2021
PolarSSL versions prior to v1.1 use the HAVEGE random number generation algorithm. At its heart, this uses timing information based on the processor's high resolution timer (the RDTSC instruction). This instruction can be virtualized, and some virtual machine hosts have chosen to disable this instruction, returning 0s or predictable results.
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Analysis
by VulDB Data Team • 10/31/2021
The vulnerability identified as CVE-2011-4574 affects PolarSSL versions prior to v1.1 and represents a critical weakness in the cryptographic random number generation mechanism. This flaw stems from the implementation of the HAVEGE (HArdware ALU GEneRator) algorithm, which relies on timing variations from the processor's high resolution timer instruction known as RDTSC (Read Time-Stamp Counter). The fundamental issue lies in how this algorithm attempts to extract entropy from hardware timing variations to generate cryptographically secure random numbers, making it susceptible to predictable outputs in virtualized environments.
The technical flaw manifests when PolarSSL employs the HAVEGE algorithm in virtual machine environments where the RDTSC instruction is either disabled or virtualized in ways that produce predictable results. This vulnerability directly maps to CWE-330, which addresses the use of insufficiently random values in cryptographic contexts. The RDTSC instruction, when virtualized, can return zero values or highly predictable sequences, undermining the randomness required for secure cryptographic operations. This weakness is particularly dangerous because it affects the core cryptographic primitives that secure communications depend upon, including key generation, session identifiers, and nonces.
The operational impact of this vulnerability extends beyond simple cryptographic weakness, as it fundamentally compromises the security assurances that PolarSSL is designed to provide. When running in virtualized environments where RDTSC returns predictable values, attackers can potentially reconstruct the random number sequences used by the cryptographic library, leading to key recovery attacks, session hijacking, and the ability to forge cryptographic signatures. This vulnerability affects any system using PolarSSL versions before v1.1 in virtualized deployments, making it particularly relevant for cloud environments, containerized applications, and virtualized infrastructure where virtual machine hosts may disable or restrict access to the RDTSC instruction for performance or security reasons.
Mitigation strategies for CVE-2011-4574 require immediate upgrades to PolarSSL version 1.1 or later, which addressed this specific weakness by improving the random number generation algorithms and providing better fallback mechanisms. Organizations should also implement proper entropy sources and consider using operating system-provided cryptographic random number generators when available. The vulnerability demonstrates the importance of considering virtualization environments when designing cryptographic systems, aligning with ATT&CK technique T1552.004, which focuses on credentials from password storage. Additionally, security practitioners should conduct regular audits of cryptographic libraries in use, ensuring that random number generation meets industry standards such as those specified in NIST SP 800-90A for cryptographic random number generation. The vulnerability also highlights the need for comprehensive testing in virtualized environments to validate the quality of entropy sources used by cryptographic implementations.