CVE-2005-2946 in OpenSSL
Summary
by MITRE
The default configuration on OpenSSL before 0.9.8 uses MD5 for creating message digests instead of a more cryptographically strong algorithm, which makes it easier for remote attackers to forge certificates with a valid certificate authority signature.
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Analysis
by VulDB Data Team • 08/04/2019
The vulnerability described in CVE-2005-2946 represents a critical cryptographic weakness in OpenSSL implementations prior to version 0.9.8. This issue stems from the default configuration using the MD5 hashing algorithm for message digest operations, which fundamentally compromises the security assurances that digital certificates are designed to provide. The use of MD5 in this context creates a significant attack surface that allows malicious actors to exploit the inherent weaknesses in the cryptographic primitive.
The technical flaw manifests in the certificate generation and validation process where MD5's known collision vulnerabilities become exploitable. MD5 has been extensively researched and demonstrated to be vulnerable to collision attacks since 2004, with practical attacks becoming feasible by 2005 when this vulnerability was discovered. The default configuration choice to use MD5 instead of stronger algorithms like SHA-1 or SHA-2 creates a scenario where attackers can generate certificates that appear to be signed by legitimate certificate authorities, effectively bypassing the trust model that public key infrastructure relies upon. This vulnerability directly maps to CWE-327, which addresses the use of weak cryptographic algorithms, and specifically targets the improper use of hash functions in security-critical contexts.
The operational impact of this vulnerability extends far beyond simple certificate forgery. Remote attackers can exploit this weakness to create fraudulent certificates that would be accepted by systems configured with the vulnerable OpenSSL versions, potentially enabling man-in-the-middle attacks, impersonation of legitimate services, and unauthorized access to sensitive communications. The attack vector is particularly dangerous because it requires no local access or special privileges, making it a remote exploit that can be executed against any system using the vulnerable OpenSSL implementation. This weakness undermines the fundamental security assumptions of SSL/TLS connections and certificate-based authentication systems, creating widespread potential for credential theft, data interception, and service disruption.
Organizations affected by this vulnerability should immediately upgrade to OpenSSL 0.9.8 or later versions where MD5 is no longer used as the default hash algorithm for certificate signatures. The recommended mitigation strategy involves comprehensive system auditing to identify all instances of vulnerable OpenSSL installations, followed by immediate patching or upgrading procedures. Security administrators should also implement monitoring for suspicious certificate activities and consider revoking certificates issued by affected systems. This vulnerability exemplifies the critical importance of cryptographic algorithm selection and the necessity of following established security standards such as those defined by NIST SP 800-131A, which recommends against the use of MD5 for digital signatures and certificate generation. The remediation process should include thorough testing of patched systems to ensure that the upgrade has not introduced compatibility issues with existing applications and services that depend on OpenSSL functionality.