CVE-2012-2417 in PyCrypto
Summary
by MITRE
PyCrypto before 2.6 does not produce appropriate prime numbers when using an ElGamal scheme to generate a key, which reduces the signature space or public key space and makes it easier for attackers to conduct brute force attacks to obtain the private key.
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Analysis
by VulDB Data Team • 12/31/2024
The vulnerability identified as CVE-2012-2417 affects the PyCrypto library version 2.6 and earlier, specifically targeting the ElGamal key generation implementation. This flaw represents a critical weakness in cryptographic randomness that fundamentally compromises the security of systems relying on this library for key generation. The issue stems from the library's inability to produce properly distributed prime numbers during the ElGamal key generation process, creating predictable patterns in the mathematical foundations of the cryptographic system.
The technical root cause of this vulnerability lies in the flawed prime number generation algorithm within the PyCrypto library's ElGamal implementation. When generating ElGamal keys, the system should produce large prime numbers that are statistically random and uniformly distributed to ensure cryptographic strength. However, the vulnerable version of PyCrypto produces prime numbers with insufficient entropy and poor distribution characteristics, effectively reducing the size of the signature space or public key space. This mathematical weakness directly violates the fundamental principles of cryptographic security where randomness and unpredictability are essential for maintaining key strength.
The operational impact of this vulnerability is severe and far-reaching across numerous systems and applications that depend on the PyCrypto library for cryptographic operations. Attackers can exploit this weakness by conducting more efficient brute force attacks against the reduced key space, significantly decreasing the computational resources and time required to recover private keys. This vulnerability affects any system where ElGamal signatures or key exchanges are implemented using the affected library version, potentially compromising digital signatures, secure communications, and authentication mechanisms. The reduced signature space makes cryptographic systems more susceptible to various attack vectors including key recovery attacks, signature forgery, and decryption attempts that would normally be computationally infeasible.
The vulnerability aligns with CWE-330, which addresses the use of insufficiently random values, and represents a classic example of poor random number generation in cryptographic contexts. From an ATT&CK framework perspective, this weakness maps to the privilege escalation and credential access phases where adversaries can leverage predictable cryptographic elements to gain unauthorized access to systems. Organizations using affected versions of PyCrypto should immediately upgrade to version 2.6 or later, which contains the corrected prime number generation algorithms. Additional mitigations include implementing proper key rotation procedures, monitoring for unauthorized cryptographic operations, and conducting comprehensive security assessments of systems that rely on this library for cryptographic functions. The fix addresses the underlying randomness issues by implementing proper prime number generation techniques that ensure adequate entropy and statistical distribution properties required for robust cryptographic security.