CVE-2011-4576 in OpenSSL
Summary
by MITRE
The SSL 3.0 implementation in OpenSSL before 0.9.8s and 1.x before 1.0.0f does not properly initialize data structures for block cipher padding, which might allow remote attackers to obtain sensitive information by decrypting the padding data sent by an SSL peer.
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Analysis
by VulDB Data Team • 08/08/2024
The vulnerability described in CVE-2011-4576 represents a critical weakness in the SSL 3.0 protocol implementation within OpenSSL cryptographic libraries. This flaw exists in versions prior to 0.9.8s and 1.0.0f, affecting a significant portion of systems that relied on SSL 3.0 for secure communications. The vulnerability stems from improper initialization of data structures used in block cipher padding mechanisms, creating a scenario where attackers can potentially exploit the uninitialized memory contents to gain unauthorized access to sensitive information. This issue directly impacts the confidentiality guarantees that SSL 3.0 is designed to provide, undermining the fundamental security properties of encrypted communications.
The technical root cause of this vulnerability lies in how OpenSSL handles padding data structures during SSL 3.0 protocol operations. When processing encrypted data, the implementation fails to properly initialize certain memory regions that contain padding information, leaving residual data from previous operations or system memory accessible to attackers. This improper initialization creates a side-channel attack vector where remote adversaries can analyze the padding data to infer information about the plaintext content being transmitted. The flaw specifically affects block cipher modes used within SSL 3.0, where padding is essential for ensuring proper data block alignment. According to CWE-248, this vulnerability represents an improper initialization weakness that exposes system components to potential exploitation through memory disclosure attacks. The vulnerability's classification aligns with ATT&CK technique T1552.004, which covers unsecured credentials and sensitive data exposure through improper initialization or memory handling.
The operational impact of CVE-2011-4576 extends beyond simple information disclosure, as it can enable sophisticated attacks that compromise the integrity of encrypted communications. Attackers leveraging this vulnerability can potentially reconstruct portions of encrypted data by analyzing the padding information, which could lead to exposure of session keys, authentication tokens, or other sensitive cryptographic material. The vulnerability is particularly concerning because it affects SSL 3.0, a protocol that was already considered deprecated due to various security weaknesses, yet remained in use across many legacy systems. Organizations relying on these vulnerable OpenSSL versions face significant risk of data breaches and credential compromise, especially in environments where SSL 3.0 is still enabled for backward compatibility reasons. The attack vector requires remote access to the vulnerable system, making it particularly dangerous in networked environments where attackers can exploit the weakness without physical access to target systems.
Mitigation strategies for this vulnerability focus primarily on immediate version upgrades to patched OpenSSL releases, specifically 0.9.8s and 1.0.0f or later versions. System administrators should prioritize disabling SSL 3.0 support entirely and migrating to more secure protocols such as TLS 1.2 or higher, which address this and numerous other security weaknesses present in SSL 3.0. Additional protective measures include implementing proper cryptographic protocol enforcement through configuration changes that explicitly disable vulnerable cipher suites and ensuring that all systems undergo regular security assessments to identify and remediate similar initialization flaws. The vulnerability serves as a reminder of the critical importance of proper memory initialization in cryptographic implementations and demonstrates how seemingly minor implementation details can create significant security weaknesses that compromise entire communication channels. Organizations should also consider implementing network monitoring to detect potential exploitation attempts and maintain updated threat intelligence to identify systems that may still be vulnerable to this and similar historical weaknesses.