CVE-2012-5791 in Invoicing
Summary
by MITRE
PayPal Invoicing does not verify that the server hostname matches a domain name in the subject s Common Name (CN) or subjectAltName field of the X.509 certificate, which allows man-in-the-middle attackers to spoof SSL servers via an arbitrary valid certificate.
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Analysis
by VulDB Data Team • 03/15/2019
The vulnerability identified as CVE-2012-5791 represents a critical SSL/TLS certificate validation flaw within PayPal's invoicing system that directly undermines the fundamental security principle of server authentication. This weakness resides in the SSL certificate verification process where the system fails to properly validate that the server's hostname matches either the Common Name field or the Subject Alternative Name fields within the X.509 certificate structure. The absence of this crucial validation step creates a significant attack surface that enables malicious actors to perform man-in-the-middle attacks by presenting any valid SSL certificate, regardless of whether it corresponds to the legitimate PayPal server.
The technical nature of this vulnerability aligns with CWE-295, which specifically addresses improper certificate validation in SSL/TLS implementations. This flaw operates at the core of the SSL/TLS protocol's security model where certificate validation should ensure that the certificate presented by a server corresponds to the domain name being accessed. When a client performs an SSL handshake with a server, it should verify that the certificate's subject fields contain domain names that match the target hostname. The PayPal system's failure to perform this verification means that attackers can intercept communications and present certificates signed by trusted Certificate Authorities but associated with different domains, effectively bypassing the intended security controls.
From an operational perspective, this vulnerability creates severe risks for users conducting invoicing transactions through PayPal's services. Attackers can exploit this weakness to intercept sensitive financial data, including invoice details, payment information, and personal identification data transmitted between users and PayPal's servers. The impact extends beyond simple data interception to potential fraud scenarios where attackers could manipulate invoice amounts, redirect payments, or gain unauthorized access to user accounts. The vulnerability particularly affects users who access PayPal's invoicing system over untrusted networks such as public Wi-Fi connections, where the man-in-the-middle attack vector becomes significantly more accessible.
The attack methodology for exploiting this vulnerability follows established patterns documented in the MITRE ATT&CK framework under the technique of credential access through man-in-the-middle attacks. An attacker positioned between a user and PayPal's server can intercept the SSL connection and present a legitimate-looking certificate that appears to be from PayPal but is actually controlled by the attacker. This allows the attacker to decrypt and modify communications, potentially altering invoice details or redirecting payment flows. The vulnerability is particularly dangerous because it affects the trust model that SSL/TLS is designed to establish, making it appear as though users are communicating securely with legitimate PayPal servers when they are actually communicating with attacker-controlled systems.
Organizations should implement multiple layers of mitigation strategies to address this vulnerability. The primary recommendation involves ensuring that all SSL/TLS implementations perform strict hostname verification against both the Common Name and Subject Alternative Name fields of certificates. This includes implementing proper certificate pinning mechanisms where applications maintain a list of trusted certificate fingerprints or public keys. Network security controls should be enhanced with deep packet inspection capabilities to detect anomalous certificate behavior, and regular security audits should verify that certificate validation is properly enforced across all systems. Additionally, users should be educated about the importance of checking certificate details manually when accessing sensitive financial services, and organizations should implement automated monitoring systems to detect potential certificate mismatches or suspicious certificate usage patterns. The remediation process requires immediate patching of affected systems and comprehensive testing to ensure that certificate validation is properly enforced throughout the entire application stack.