CVE-2008-0299 in Paramiko
Summary
by MITRE
common.py in Paramiko 1.7.1 and earlier, when using threads or forked processes, does not properly use RandomPool, which allows one session to obtain sensitive information from another session by predicting the state of the pool.
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Analysis
by VulDB Data Team • 08/06/2019
The vulnerability described in CVE-2008-0299 represents a critical cryptographic weakness in the Paramiko SSH library version 1.7.1 and earlier. This issue stems from improper implementation of the RandomPool mechanism within the common.py module, which is fundamental to generating secure random numbers for cryptographic operations. The flaw becomes particularly dangerous when the library operates in multi-threaded environments or when processes are forked, as these scenarios create conditions where random number generation becomes predictable and vulnerable to cross-session information leakage.
The technical root cause of this vulnerability lies in the inadequate synchronization and state management of the RandomPool object across concurrent execution contexts. When multiple threads or forked processes utilize the same RandomPool instance, the internal state becomes corrupted or predictable, allowing an attacker to reverse-engineer the random number sequence used by other sessions. This predictability compromises the cryptographic security of the SSH connections, as random numbers are essential for generating secure session keys, nonces, and other cryptographic parameters that protect against various attacks including session hijacking and key recovery attacks. The vulnerability specifically targets the cryptographic randomness generation mechanism, which is classified under CWE-330 Use of Insufficiently Random Values in the Common Weakness Enumeration catalog.
The operational impact of this vulnerability extends beyond simple information disclosure, as it fundamentally undermines the security assurances provided by SSH encryption. An attacker who can predict the state of the RandomPool can potentially reconstruct session keys, impersonate legitimate users, or decrypt previously captured network traffic. This makes the vulnerability particularly dangerous in environments where multiple SSH sessions are established simultaneously or where the library is used in high-concurrency applications. The risk is amplified in scenarios involving process forking, which is common in web applications and server environments where child processes are created to handle concurrent requests. According to ATT&CK framework, this vulnerability maps to technique T1552.001 (Unsecured Credentials) and T1071.004 (Application Layer Protocol: SSH), as it compromises the integrity of credential protection mechanisms and allows for protocol-level attacks against SSH implementations.
Mitigation strategies for this vulnerability require immediate upgrading to Paramiko versions 1.7.2 or later, where the RandomPool implementation has been corrected to properly handle concurrent access and maintain cryptographic security. Organizations should also implement proper random number generation practices in their applications, ensuring that cryptographic operations do not rely on shared state or predictable sequences. Additional defensive measures include monitoring for unusual patterns in SSH session establishment and implementing network-level controls to detect potential exploitation attempts. The vulnerability highlights the critical importance of proper concurrent programming practices in cryptographic libraries and demonstrates how seemingly minor implementation flaws can have severe security implications. System administrators should conduct thorough audits of all systems using affected Paramiko versions and ensure that proper patch management procedures are in place to address similar vulnerabilities in other cryptographic libraries.