CVE-2016-2176 in Communications
Summary
by MITRE
The X509_NAME_oneline function in crypto/x509/x509_obj.c in OpenSSL before 1.0.1t and 1.0.2 before 1.0.2h allows remote attackers to obtain sensitive information from process stack memory or cause a denial of service (buffer over-read) via crafted EBCDIC ASN.1 data.
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Analysis
by VulDB Data Team • 04/09/2023
The vulnerability identified as CVE-2016-2176 represents a critical security flaw in OpenSSL's X509_NAME_oneline function that affects multiple versions of the cryptographic library. This issue stems from improper handling of EBCDIC encoded ASN.1 data structures during certificate processing, creating potential pathways for both information disclosure and denial of service attacks. The vulnerability exists within the crypto/x509/x509_obj.c source file and impacts OpenSSL versions prior to 1.0.1t and 1.0.2h, making it a widespread concern across numerous systems that rely on OpenSSL for secure communications.
The technical flaw manifests when the X509_NAME_oneline function processes crafted EBCDIC ASN.1 data, leading to a buffer over-read condition that can expose sensitive stack memory contents to remote attackers. This occurs because the function does not properly validate the length of input data before attempting to parse EBCDIC encoded structures, allowing malicious actors to craft specific ASN.1 sequences that cause the parser to read beyond allocated memory boundaries. The vulnerability specifically targets the EBCDIC character encoding handling within the X509_NAME structure processing, where the function assumes certain data formats without adequate bounds checking, creating a classic buffer over-read scenario that can be exploited through carefully constructed certificate data.
From an operational perspective, this vulnerability presents significant risks to systems relying on OpenSSL for SSL/TLS operations, certificate validation, and secure communications. Attackers can leverage this flaw to either extract sensitive information from process memory, potentially including cryptographic keys, session data, or other confidential information, or to cause denial of service conditions that disrupt legitimate service operations. The impact extends beyond simple information disclosure, as the buffer over-read can lead to application crashes, system instability, and potentially provide attackers with footholds for more sophisticated attacks. Systems processing X509 certificates from untrusted sources, such as web servers, email servers, or any application that validates certificates, are particularly vulnerable to exploitation.
The vulnerability maps directly to CWE-121, which describes heap-based buffer overflow conditions, and aligns with several ATT&CK techniques including T1059 for command and script injection and T1499 for network denial of service. Organizations should implement immediate mitigations by upgrading to OpenSSL versions 1.0.1t or 1.0.2h, which contain patches addressing the buffer over-read issue. Additionally, network segmentation, certificate validation hardening, and monitoring for unusual certificate processing patterns should be implemented as defensive measures. Regular security assessments and vulnerability scanning should be conducted to identify systems that may still be running vulnerable versions of OpenSSL, as this vulnerability can remain undetected for extended periods while continuing to pose risks to system integrity and confidentiality.
This vulnerability demonstrates the critical importance of proper input validation and bounds checking in cryptographic libraries, where seemingly minor parsing issues can lead to severe security consequences. The EBCDIC handling specifically highlights the complexity of supporting multiple character encodings in cryptographic applications and the need for comprehensive testing across various data formats. Organizations should also consider implementing certificate transparency monitoring and automated patch management processes to ensure timely remediation of similar vulnerabilities in cryptographic libraries and other security-critical components.