CVE-2004-0765 in Firefox
Summary
by MITRE
The cert_TestHostName function in Mozilla before 1.7, Firefox before 0.9, and Thunderbird before 0.7, only checks the hostname portion of a certificate when the hostname portion of the URI is not a fully qualified domain name (FQDN), which allows remote attackers to spoof trusted certificates.
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Analysis
by VulDB Data Team • 05/31/2019
The vulnerability described in CVE-2004-0765 represents a critical certificate validation flaw in Mozilla's security implementation that persisted across multiple widely-used applications including the Mozilla browser, Firefox, and Thunderbird. This weakness specifically affects versions prior to Mozilla 1.7, Firefox 0.9, and Thunderbird 0.7, creating a significant security gap that could be exploited by malicious actors to bypass important SSL/TLS certificate verification mechanisms. The flaw resides in the cert_TestHostName function which governs how hostnames are validated against SSL certificates during secure communications.
The technical nature of this vulnerability stems from an incomplete hostname validation algorithm that fails to properly verify certificate subject names when the URI hostname lacks a fully qualified domain name structure. In standard secure communications, when a client connects to a server using HTTPS, the client must validate that the certificate presented by the server matches the hostname specified in the URL. The function in question only performs a partial validation of the hostname portion of certificates, specifically when the URI hostname is not a fully qualified domain name. This incomplete validation creates a window where attackers can present certificates that appear to be from legitimate domains but contain different subject information, effectively allowing for certificate spoofing attacks.
This vulnerability directly impacts the fundamental security guarantees provided by SSL/TLS certificates and falls under the category of certificate validation failures that compromise the integrity of secure communications. The operational impact is severe as it allows remote attackers to conduct man-in-the-middle attacks by presenting certificates that would normally be rejected by proper validation mechanisms. An attacker could potentially create a certificate that matches the partial hostname portion but differs in other components such as the domain suffix or organizational identifiers, thus fooling the validation process and establishing trust in a fraudulent certificate.
The weakness manifests as a failure to properly implement certificate hostname validation according to established security standards and best practices. This flaw aligns with CWE-295, which addresses improper certificate validation, and represents a specific implementation issue in the certificate verification process. From an attack perspective, this vulnerability enables threat actors to exploit the trust model inherent in web browsers and email clients, potentially leading to data interception, session hijacking, and credential theft. The impact extends beyond individual user sessions to potentially compromise entire organizations that rely on secure communications for business operations.
Organizations and users should immediately update to patched versions of Mozilla applications to remediate this vulnerability. The fix typically involves implementing complete hostname validation that properly compares the certificate subject name against the URI hostname regardless of whether the hostname is a fully qualified domain name. System administrators should also consider implementing additional security measures such as certificate pinning for critical applications, monitoring for suspicious certificate usage, and maintaining awareness of certificate validation best practices. This vulnerability underscores the importance of comprehensive security testing and validation of cryptographic implementations in widely-deployed software applications.