CVE-2013-4314 in pyOpenSSL
Summary
by MITRE
The X509Extension in pyOpenSSL before 0.13.1 does not properly handle a \0 character in a domain name in the Subject Alternative Name field of an X.509 certificate, which allows man-in-the-middle attackers to spoof arbitrary SSL servers via a crafted certificate issued by a legitimate Certification Authority.
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Analysis
by VulDB Data Team • 12/25/2024
The vulnerability identified as CVE-2013-4314 affects the pyOpenSSL library version 0.13.1 and earlier, specifically targeting the X509Extension component that processes X.509 certificates. This flaw resides in the certificate validation logic where the library fails to properly handle null character sequences within domain names contained in the Subject Alternative Name field. The issue stems from inadequate input sanitization and validation mechanisms that should have prevented malformed certificate data from being processed correctly during SSL/TLS certificate verification operations.
The technical implementation of this vulnerability occurs when pyOpenSSL encounters an X.509 certificate containing a null character within a domain name string in the Subject Alternative Name extension. This null character, represented as , creates a parsing anomaly that bypasses standard certificate validation checks. The flaw allows attackers to craft malicious certificates that appear valid to the vulnerable library while containing deceptive domain name entries that can be used to establish fraudulent SSL connections. This represents a critical weakness in the certificate validation chain that undermines the fundamental security guarantees provided by public key infrastructure.
The operational impact of this vulnerability creates significant risks for systems relying on pyOpenSSL for SSL/TLS certificate validation. Attackers can exploit this weakness to perform man-in-the-middle attacks by presenting certificates that contain null characters in domain names, effectively bypassing certificate validation mechanisms. This allows malicious actors to impersonate legitimate web services and intercept encrypted communications without detection. The vulnerability specifically targets the trust model of SSL/TLS implementations, potentially compromising the confidentiality and integrity of data transmitted over secure connections. Organizations using affected versions of pyOpenSSL face elevated risk of credential theft, data interception, and service disruption attacks.
Mitigation strategies for CVE-2013-4314 require immediate upgrade to pyOpenSSL version 0.13.1 or later, which includes proper null character handling in X.509 extension processing. Security administrators should conduct comprehensive inventory audits to identify all systems utilizing vulnerable pyOpenSSL versions and prioritize patch deployment across all affected environments. Additional defensive measures include implementing certificate pinning mechanisms, monitoring for suspicious certificate issuance patterns, and enhancing network traffic inspection capabilities to detect anomalous SSL/TLS handshakes. The vulnerability aligns with CWE-170, which addresses improper null termination handling, and maps to ATT&CK technique T1552.001 for credential access through the exploitation of certificate validation weaknesses, making it a critical target for both preventive and detective security controls.