CVE-2011-2705 in Ruby
Summary
by MITRE
The SecureRandom.random_bytes function in lib/securerandom.rb in Ruby before 1.8.7-p352 and 1.9.x before 1.9.2-p290 relies on PID values for initialization, which makes it easier for context-dependent attackers to predict the result string by leveraging knowledge of random strings obtained in an earlier process with the same PID.
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Analysis
by VulDB Data Team • 11/17/2021
The vulnerability described in CVE-2011-2705 affects the SecureRandom.random_bytes function implementation within Ruby's standard library, specifically impacting versions prior to 1.8.7-p352 and 1.9.2-p290. This flaw resides in the lib/securerandom.rb file where the random number generation mechanism fails to properly initialize its entropy sources, creating a predictable cryptographic weakness that directly impacts applications relying on secure random number generation for cryptographic operations. The vulnerability stems from the implementation's dependence on process identifier values as part of its initialization sequence, which fundamentally undermines the randomness properties required for cryptographic security.
The technical flaw manifests when the SecureRandom function initializes its internal state using process ID values as entropy sources rather than properly seeded cryptographic random number generators. This approach creates a deterministic pattern where attackers can predict future random values by observing previously generated random strings from processes that share the same PID. The vulnerability specifically affects cryptographic applications that depend on secure random number generation for session tokens, encryption keys, nonce values, and other security-critical components. When multiple processes with identical PIDs are executed, particularly in environments where process recycling occurs frequently, attackers can correlate random outputs across different execution contexts to reconstruct the underlying random number generation state.
The operational impact of this vulnerability extends beyond simple predictability issues to encompass serious cryptographic risks that can compromise entire security systems. Applications using vulnerable Ruby versions may experience session hijacking, key compromise, and nonce reuse attacks that can lead to full system compromise. The context-dependent nature of this vulnerability means that attackers need only observe random outputs from a previous process with the same PID to begin predicting subsequent outputs, making this particularly dangerous in multi-process environments or when applications are restarted with recycled process identifiers. This weakness directly violates the fundamental principles of cryptographic randomness as defined by industry standards and best practices, creating a significant attack surface for malicious actors.
Mitigation strategies for CVE-2011-2705 require immediate version upgrades to Ruby 1.8.7-p352 or 1.9.2-p290, which contain the necessary patches to properly initialize random number generators using appropriate entropy sources. Organizations should also implement comprehensive code review processes to identify all applications and libraries that may be using the vulnerable SecureRandom functionality, particularly those handling cryptographic operations, session management, and key generation. System administrators should monitor for process recycling patterns that could exacerbate the vulnerability and consider implementing additional entropy sources or hardware random number generators for critical security applications. This vulnerability aligns with CWE-330, which addresses insufficient entropy in random number generation, and represents a specific implementation weakness that can be exploited through techniques categorized under ATT&CK tactic TA0006, privilege escalation, and TA0004, privilege escalation, through predictable random number generation attacks. The remediation process should include thorough testing of upgraded environments to ensure that the patched SecureRandom implementation properly utilizes system entropy sources and maintains cryptographic strength for all security-sensitive operations.