CVE-2002-0659 in OpenSSL
Summary
by MITRE
The ASN1 library in OpenSSL 0.9.6d and earlier, and 0.9.7-beta2 and earlier, allows remote attackers to cause a denial of service via invalid encodings.
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Analysis
by VulDB Data Team • 09/14/2025
The vulnerability identified as CVE-2002-0659 represents a critical denial of service flaw within the ASN1 library component of OpenSSL versions 0.9.6d and earlier, as well as 0.9.7-beta2 and earlier releases. This issue stems from inadequate validation of ASN1 (Abstract Syntax Notation One) encodings during the processing of cryptographic data structures, specifically affecting the parsing and handling of malformed data sequences. The ASN1 library serves as a fundamental component in OpenSSL responsible for encoding and decoding data structures used in various cryptographic protocols including SSL/TLS, X.509 certificates, and PKCS standards. When encountering invalid or malformed ASN1 encodings, the library fails to properly handle the error conditions, leading to system instability and potential service disruption.
The technical nature of this vulnerability places it under CWE-129, which specifically addresses improper validation of array index values, and more broadly relates to CWE-248, which covers exposure of an exception to external processes. The flaw occurs during the ASN1 parsing phase where the library does not adequately validate input data before attempting to process it, allowing attackers to craft specially malformed ASN1 structures that trigger memory corruption or infinite loop conditions. This type of vulnerability falls within the ATT&CK framework under TA0043 (Reconnaissance) and TA0045 (Execution) as attackers can first discover the vulnerable system through reconnaissance activities and then exploit the vulnerability to execute denial of service attacks. The attack vector requires remote access to systems utilizing vulnerable OpenSSL versions, where attackers can send maliciously crafted ASN1 encoded data through network connections that rely on OpenSSL for cryptographic operations.
The operational impact of CVE-2002-0659 extends beyond simple service interruption, as it can affect critical infrastructure components that depend on OpenSSL for secure communications. Systems running vulnerable versions may experience complete service unavailability, application crashes, or resource exhaustion, particularly when the vulnerability is exploited in high-traffic environments or in applications that process large volumes of cryptographic data. The vulnerability affects not only web servers but also email servers, database systems, and any application that employs OpenSSL for secure communication protocols. Organizations using older OpenSSL versions are particularly at risk since the vulnerability exists in the core ASN1 parsing functionality that is utilized across multiple cryptographic operations. The exploitation of this vulnerability can lead to significant business disruption, as service availability is compromised and may require system restarts or complete reconfiguration to restore normal operations.
Mitigation strategies for CVE-2002-0659 primarily focus on immediate version upgrades to patched OpenSSL releases, specifically OpenSSL 0.9.7a and later versions that contain the necessary fixes for the ASN1 parsing issues. System administrators should conduct comprehensive vulnerability assessments to identify all systems running vulnerable OpenSSL versions and prioritize patching activities accordingly. Additional defensive measures include implementing network-based intrusion detection systems that can identify and block malformed ASN1 traffic patterns, as well as configuring application-level input validation to filter out suspicious data before it reaches the OpenSSL library. Organizations should also consider implementing network segmentation and access controls to limit exposure of vulnerable systems to untrusted networks. The remediation process requires careful testing of patched versions in staging environments to ensure compatibility with existing applications and services. Security monitoring should be enhanced to detect unusual patterns of service disruption that may indicate exploitation attempts, and incident response procedures should be updated to include specific protocols for handling ASN1-related denial of service attacks. Regular security audits and vulnerability scanning should be implemented to maintain awareness of similar vulnerabilities in other cryptographic libraries and system components that may present analogous risks.