CVE-2011-4619 in OpenSSL
Summary
by MITRE
The Server Gated Cryptography (SGC) implementation in OpenSSL before 0.9.8s and 1.x before 1.0.0f does not properly handle handshake restarts, which allows remote attackers to cause a denial of service (CPU consumption) via unspecified vectors.
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Analysis
by VulDB Data Team • 08/08/2024
The vulnerability identified as CVE-2011-4619 resides within the Server Gated Cryptography implementation of OpenSSL, a critical component in secure communications infrastructure. This flaw affects versions prior to 0.9.8s and 1.x before 1.0.0f, representing a significant security gap that could be exploited by remote attackers to compromise system availability. The issue specifically manifests during the SSL/TLS handshake process where the SGC implementation fails to correctly manage handshake restart scenarios, creating a condition that can be manipulated to consume excessive CPU resources.
The technical root cause of this vulnerability stems from improper handling of handshake restarts within the SGC cryptographic framework. When a client and server attempt to establish a secure connection using SGC protocols, the handshake process involves multiple steps where cryptographic parameters are negotiated and validated. In vulnerable versions of OpenSSL, if a handshake restart occurs during this process, the implementation does not properly reset or validate the cryptographic state, leading to a condition where the server continues to process the incomplete handshake indefinitely. This results in a resource exhaustion scenario where the server's CPU cycles are consumed in an endless loop of handshake processing attempts.
From an operational impact perspective, this vulnerability presents a severe denial of service risk that can effectively cripple affected systems. Attackers can exploit this weakness by initiating multiple handshake sequences that trigger the problematic code path, causing the targeted server to consume excessive CPU resources and potentially become unresponsive to legitimate connection requests. The vulnerability is particularly concerning because it can be triggered without requiring authentication or specific privileges, making it an attractive target for automated attacks and large-scale denial of service campaigns. Systems running vulnerable OpenSSL versions may experience complete service disruption, impacting availability for legitimate users and potentially causing cascading failures in larger network infrastructures.
The mitigation strategy for CVE-2011-4619 centers on immediate patching of affected OpenSSL installations to versions 0.9.8s or 1.0.0f and later. Organizations should conduct comprehensive inventory assessments to identify all systems running vulnerable OpenSSL versions and prioritize patch deployment across their infrastructure. Network administrators should also consider implementing rate limiting and connection throttling mechanisms to reduce the impact of potential exploitation attempts. Additionally, monitoring systems should be configured to detect unusual CPU consumption patterns that might indicate exploitation of this vulnerability. This remediation approach aligns with industry best practices for vulnerability management and follows the principle of least privilege by ensuring that cryptographic implementations properly handle all possible handshake scenarios including restart conditions. The vulnerability demonstrates the importance of thorough testing of cryptographic implementations and proper state management during security protocol negotiations, as outlined in common weakness enumerations such as CWE-362 and attack patterns documented in the MITRE ATT&CK framework for privilege escalation and denial of service techniques.