CVE-2015-1793 in JD Edwards World Security
Summary
by MITRE
The X509_verify_cert function in crypto/x509/x509_vfy.c in OpenSSL 1.0.1n, 1.0.1o, 1.0.2b, and 1.0.2c does not properly process X.509 Basic Constraints cA values during identification of alternative certificate chains, which allows remote attackers to spoof a Certification Authority role and trigger unintended certificate verifications via a valid leaf certificate.
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Analysis
by VulDB Data Team • 06/25/2024
The vulnerability identified as CVE-2015-1793 represents a critical flaw in OpenSSL's certificate verification process that specifically affects versions 1.0.1n, 1.0.1o, 1.0.2b, and 1.0.2c. This issue resides within the X509_verify_cert function located in the crypto/x509/x509_vfy.c file, where the implementation fails to correctly handle X.509 Basic Constraints extension values. The Basic Constraints extension is a crucial component of X.509 certificates that determines whether a certificate can serve as a Certificate Authority, with the cA (certification authority) boolean field indicating this capability. When this field is properly set to true, it signifies that the certificate holder can issue other certificates and act as a CA. The flaw occurs during the alternative certificate chain identification process, where OpenSSL should validate that certificates in the chain properly inherit the CA capabilities from their issuers.
The technical nature of this vulnerability stems from improper validation of the cA flag within the certificate verification algorithm, allowing attackers to manipulate certificate chains in ways that should not be permitted under standard X.509 certificate validation rules. An attacker can construct a certificate chain where a non-CA certificate appears to have CA capabilities through manipulation of the Basic Constraints extension, effectively bypassing the normal certificate hierarchy validation. This misconfiguration creates a scenario where a valid leaf certificate can be used to spoof a CA role, enabling the attacker to generate certificates that appear legitimate to systems using vulnerable OpenSSL implementations. The vulnerability specifically impacts the certificate chain validation logic that should enforce the hierarchical nature of certificate authorities, where intermediate certificates must properly declare their CA capabilities to validate subordinate certificates.
The operational impact of CVE-2015-1793 is severe and far-reaching, as it allows remote attackers to perform man-in-the-middle attacks and certificate spoofing operations across systems using vulnerable OpenSSL versions. This vulnerability can be exploited in various contexts including web browsers, email clients, and any application that relies on OpenSSL for SSL/TLS certificate validation. The ability to spoof CA roles means that attackers can potentially create certificates that appear to be issued by trusted Certificate Authorities, leading to successful phishing attacks, data interception, and unauthorized access to protected systems. The vulnerability is particularly dangerous because it operates at the core validation layer of SSL/TLS implementations, making it difficult to detect and potentially allowing attackers to remain undetected while conducting malicious activities. This flaw directly violates the fundamental security principles of certificate-based authentication systems and can compromise the entire trust infrastructure of affected applications.
Mitigation strategies for CVE-2015-1793 require immediate patching of affected OpenSSL versions to the latest stable releases that contain the corrected certificate verification logic. Organizations should prioritize updating all systems running vulnerable OpenSSL versions and conduct thorough testing to ensure that the patches do not introduce compatibility issues with existing applications. The fix implemented in subsequent OpenSSL releases addresses the specific validation issue in the X509_verify_cert function by ensuring that the cA flag is properly enforced during certificate chain validation, preventing certificates from incorrectly inheriting CA capabilities. Security administrators should also implement monitoring for suspicious certificate validation behaviors and consider deploying additional security controls such as certificate pinning to reduce the impact of potential exploitation. This vulnerability aligns with CWE-295 which addresses improper certificate validation and relates to ATT&CK technique T1552.001 for credentials from password storage, as it enables attackers to compromise the certificate-based authentication mechanisms that protect sensitive communications and data. Organizations must also review their certificate management practices and ensure that proper certificate lifecycle management procedures are in place to prevent exploitation of similar validation weaknesses in the future.