CVE-2011-0014 in OpenSSL
Summary
by MITRE
ssl/t1_lib.c in OpenSSL 0.9.8h through 0.9.8q and 1.0.0 through 1.0.0c allows remote attackers to cause a denial of service (crash), and possibly obtain sensitive information in applications that use OpenSSL, via a malformed ClientHello handshake message that triggers an out-of-bounds memory access, aka "OCSP stapling vulnerability."
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Analysis
by VulDB Data Team • 02/01/2019
The vulnerability identified as CVE-2011-0014 represents a critical out-of-bounds memory access flaw within the OpenSSL cryptographic library that affects versions ranging from 0.9.8h through 0.9.8q and 1.0.0 through 1.0.0c. This issue specifically manifests during the SSL/TLS handshake process when processing malformed ClientHello messages, creating a scenario where remote attackers can exploit the vulnerability to cause system crashes or potentially gain access to sensitive memory contents. The flaw resides in the ssl/t1_lib.c source file, which handles TLS protocol implementation details including OCSP stapling functionality. According to CWE-125, this vulnerability constitutes an out-of-bounds read condition that can lead to arbitrary code execution or information disclosure, making it particularly dangerous for systems relying on OpenSSL for secure communications.
The technical implementation of this vulnerability occurs when OpenSSL processes a specially crafted ClientHello message that includes malformed OCSP stapling data. During the handshake negotiation phase, the library fails to properly validate the length and structure of the stapling information, leading to an attempt to access memory locations beyond the allocated buffer boundaries. This improper bounds checking creates a predictable crash pattern that can be reliably triggered by remote attackers without requiring authentication or privileged access. The vulnerability affects applications that utilize OpenSSL's TLS implementation, including web servers, email servers, and any service that employs SSL/TLS encryption for secure data transmission. The flaw demonstrates characteristics consistent with ATT&CK technique T1210, which involves exploitation of vulnerabilities in remote services to achieve system compromise through denial of service or information disclosure attacks.
The operational impact of this vulnerability extends beyond simple denial of service scenarios, as it can potentially expose sensitive information from the memory space of affected applications. When the out-of-bounds memory access occurs, it may inadvertently reveal cryptographic keys, session information, or other confidential data that could be leveraged by attackers for more sophisticated attacks. The vulnerability affects a wide range of systems including web servers, database servers, and network infrastructure devices that rely on OpenSSL for secure communications. Organizations running vulnerable versions of OpenSSL face significant risk of service disruption and potential data breaches, particularly in environments where the affected applications handle sensitive information. The vulnerability's remote exploitability means that attackers can target systems from anywhere on the network without requiring physical access or local privileges. This makes it particularly dangerous for public-facing services such as web servers, email servers, and other internet-accessible applications that are commonly targeted in large-scale attacks. The flaw underscores the importance of proper input validation and bounds checking in cryptographic libraries, as well as the necessity of timely security updates to protect against known vulnerabilities. Organizations should prioritize immediate patching of affected systems and implement network monitoring to detect exploitation attempts, while also considering the broader implications for their security posture and incident response procedures.