CVE-2011-4121 in Ruby
Summary
by MITRE
The OpenSSL extension of Ruby (Git trunk) versions after 2011-09-01 up to 2011-11-03 always generated an exponent value of '1' to be used for private RSA key generation. A remote attacker could use this flaw to bypass or corrupt integrity of services, depending on strong private RSA keys generation mechanism.
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Analysis
by VulDB Data Team • 02/28/2024
The vulnerability identified as CVE-2011-4121 represents a critical flaw in the OpenSSL extension of Ruby programming language that affected versions released between September 1, 2011, and November 3, 2011. This issue fundamentally compromised the cryptographic security of RSA key generation processes within the Ruby environment, creating a significant weakness that could be exploited by malicious actors to undermine the integrity of cryptographic services relying on RSA encryption. The flaw specifically targeted the private key generation mechanism, where the system consistently used an exponent value of '1' instead of the standard cryptographic values such as 65537 or other secure primes.
The technical implementation of this vulnerability stems from a deliberate coding error in the OpenSSL extension's RSA key generation algorithm. Normally, RSA private key generation requires careful selection of cryptographic parameters including appropriate public exponents that ensure mathematical security properties and resistance against various attack vectors. When the system consistently generated keys with an exponent of '1', it created mathematically weak RSA keys that could be easily broken or manipulated by attackers. This particular flaw aligns with CWE-327, which addresses the use of weak cryptographic algorithms and improper implementation of cryptographic functions, and represents a direct violation of cryptographic best practices that require robust key generation mechanisms.
The operational impact of this vulnerability extends beyond simple cryptographic weakness to encompass broader security implications for any service or application that relies on RSA key generation within the affected Ruby environment. Remote attackers could exploit this flaw to compromise the integrity of encrypted communications, digital signatures, and authentication mechanisms that depend on RSA keys. The vulnerability particularly affects services where strong cryptographic keys are essential for maintaining security boundaries, including secure web communications, code signing, and certificate-based authentication systems. This weakness could enable attackers to forge digital signatures, decrypt sensitive communications, or perform man-in-the-middle attacks against systems using the affected Ruby versions.
Mitigation strategies for CVE-2011-4121 require immediate patching of affected Ruby installations to ensure proper RSA key generation with appropriate cryptographic exponents. System administrators should prioritize updating their Ruby environments to versions released after November 3, 2011, when the fix was implemented. Additionally, organizations should conduct comprehensive inventory assessments to identify all systems running affected Ruby versions and perform cryptographic key rotation for any services that may have been impacted. The vulnerability demonstrates the critical importance of proper cryptographic implementation and highlights the need for regular security audits of cryptographic libraries and extensions. This issue also underscores the ATT&CK framework concept of privilege escalation through cryptographic weaknesses, where attackers can leverage mathematical flaws to gain unauthorized access or manipulate system integrity. Organizations should implement monitoring systems to detect potential exploitation attempts and maintain updated security patches to prevent similar vulnerabilities from compromising their cryptographic infrastructure.