CVE-2015-5276 in gcc
Summary
by MITRE
The std::random_device class in libstdc++ in the GNU Compiler Collection (aka GCC) before 4.9.4 does not properly handle short reads from blocking sources, which makes it easier for context-dependent attackers to predict the random values via unspecified vectors.
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Analysis
by VulDB Data Team • 06/27/2022
The vulnerability identified as CVE-2015-5276 resides within the std::random_device implementation in libstdc++ component of the GNU Compiler Collection, affecting GCC versions prior to 4.9.4. This flaw specifically targets the random number generation capabilities that are fundamental to cryptographic security and system reliability. The issue manifests when the random device encounters short reads from blocking sources, creating predictable patterns in what should be cryptographically secure random sequences. The vulnerability's impact extends beyond simple randomness degradation as it directly compromises the entropy sources that modern applications depend upon for secure operations including session management, cryptographic key generation, and security protocol implementations.
The technical flaw stems from improper handling of I/O operations when reading from random number sources such as /dev/random or /dev/urandom on Unix-like systems. When these blocking sources return fewer bytes than requested during read operations, the std::random_device implementation fails to properly account for this shortfall, leading to repeated or predictable values in the generated sequences. This behavior creates a significant weakness in the entropy collection process that adversaries can exploit through unspecified vectors to reverse engineer or predict future random values. The vulnerability essentially allows attackers to observe patterns in random number generation that should remain unpredictable, fundamentally undermining the security guarantees that applications rely upon.
From an operational standpoint, this vulnerability creates substantial risk for applications that depend on secure random number generation for cryptographic operations, session tokens, nonce values, and other security-sensitive data. The context-dependent nature of the attack means that exploitation requires specific conditions where the attacker can observe or influence the random number generation process, but once successful, the impact can be severe. Applications using affected GCC versions may experience compromised session management, weakened encryption key generation, and predictable security tokens that can be easily guessed or reconstructed by malicious actors. This vulnerability particularly affects systems running applications compiled with older GCC versions where the random number generation is critical to maintaining security boundaries.
Mitigation strategies for CVE-2015-5276 primarily involve upgrading to GCC version 4.9.4 or later where the implementation properly handles short reads from blocking sources. System administrators should prioritize patching affected compilers and rebuilding all applications that rely on secure random number generation. Additionally, organizations should implement monitoring for applications that may be using vulnerable versions of GCC and consider alternative random number generation libraries or approaches for critical security applications. The vulnerability aligns with CWE-330 use of insufficiently random values and relates to ATT&CK technique T1083 for discovering system information and T1059 for system command execution that could be used to exploit predictable randomness patterns. Organizations should also implement proper entropy monitoring and consider using hardware random number generators or cryptographic libraries that provide better guarantees for secure random number generation.