CVE-2015-0285 in OpenSSL
Summary
by MITRE
The ssl3_client_hello function in s3_clnt.c in OpenSSL 1.0.2 before 1.0.2a does not ensure that the PRNG is seeded before proceeding with a handshake, which makes it easier for remote attackers to defeat cryptographic protection mechanisms by sniffing the network and then conducting a brute-force attack.
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Analysis
by VulDB Data Team • 04/15/2022
The vulnerability identified as CVE-2015-0285 represents a critical weakness in OpenSSL's SSL/TLS implementation that fundamentally undermines cryptographic security during the initial handshake process. This flaw exists within the ssl3_client_hello function located in the s3_clnt.c source file, affecting OpenSSL versions 1.0.2 prior to 1.0.2a. The core issue stems from the improper initialization sequence of the pseudorandom number generator that is essential for generating secure cryptographic keys and nonces during SSL/TLS negotiations. When a client initiates an SSL handshake, the system must first seed its random number generator with sufficient entropy to ensure unpredictability of cryptographic values. However, this particular vulnerability allows the handshake to proceed without ensuring proper seeding has occurred, creating a window of opportunity for attackers to exploit the predictable nature of the cryptographic operations.
The operational impact of CVE-2015-0285 extends beyond simple cryptographic weakness to represent a significant threat to the integrity of secure communications. Attackers can leverage this vulnerability through passive network sniffing to capture handshake data, then employ brute-force techniques to deduce the cryptographic keys used in the SSL/TLS session. This attack vector aligns with the ATT&CK framework's technique T1046 for network service scanning and T1566 for credential access through network sniffing. The vulnerability essentially creates a scenario where the random number generator's output becomes predictable, making it significantly easier for adversaries to perform cryptographic attacks such as key recovery or session hijacking. This weakness particularly affects protocols that rely heavily on random values for session key generation, making it a critical concern for any system handling sensitive data over SSL/TLS connections.
This vulnerability maps directly to CWE-330, which specifically addresses the use of insufficiently random values in cryptographic contexts. The flaw demonstrates poor entropy management and inadequate initialization of cryptographic components, which are fundamental requirements for maintaining security in TLS implementations. The issue is particularly dangerous because it operates at the protocol level during the handshake phase, meaning that any connection established through vulnerable OpenSSL versions may be susceptible to cryptographic attacks. Organizations using affected OpenSSL versions face the risk of complete session compromise, where attackers can potentially decrypt communications, impersonate legitimate parties, or conduct man-in-the-middle attacks. The vulnerability's impact is exacerbated by the fact that it requires no special privileges or access to the target system, making it a particularly attractive attack vector for remote adversaries who can simply monitor network traffic to gather the necessary information for their brute-force attempts.
Mitigation strategies for CVE-2015-0285 focus primarily on immediate software updates to OpenSSL 1.0.2a or later versions that properly address the random number generator seeding issue. System administrators should prioritize patching all affected systems and verify that the updated OpenSSL libraries are functioning correctly with proper entropy sources. Additional protective measures include implementing proper entropy gathering mechanisms such as hardware random number generators or ensuring that systems have adequate sources of entropy available during the SSL/TLS handshake process. Network monitoring solutions should be enhanced to detect anomalous handshake patterns that might indicate exploitation attempts, and organizations should consider implementing certificate pinning mechanisms as an additional layer of defense. The vulnerability highlights the importance of proper cryptographic library maintenance and demonstrates why continuous security auditing of cryptographic components is essential for maintaining secure communications infrastructure.