CVE-2000-0406 in Communicator
Summary
by MITRE
Netscape Communicator before version 4.73 and Navigator 4.07 do not properly validate SSL certificates, which allows remote attackers to steal information by redirecting traffic from a legitimate web server to their own malicious server, aka the "Acros-Suencksen SSL" vulnerability.
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Analysis
by VulDB Data Team • 04/21/2026
The CVE-2000-0406 vulnerability represents a critical SSL certificate validation flaw that affected Netscape Communicator versions prior to 4.73 and Navigator 4.07. This vulnerability stems from inadequate certificate validation mechanisms within the SSL/TLS implementation, creating a significant security gap that adversaries could exploit to conduct man-in-the-middle attacks. The flaw specifically manifests when the browser fails to properly verify certificate authenticity, allowing attackers to manipulate secure connections without detection.
This vulnerability operates through a sophisticated redirection attack vector where malicious actors can intercept legitimate web traffic and redirect it to compromised servers. The attack exploits the trust model inherent in SSL certificates by bypassing proper validation checks that should occur during the certificate handshake process. When users attempt to access legitimate websites, their connections may be silently redirected to attacker-controlled servers that present fraudulent certificates. The vulnerability is particularly dangerous because it occurs at the SSL layer, making it invisible to end users who remain unaware that their secure connections have been compromised.
The operational impact of this vulnerability extends beyond simple information theft, encompassing complete session hijacking and credential interception capabilities. Attackers can leverage this flaw to capture sensitive data transmitted over SSL connections, including login credentials, personal information, and financial data. The vulnerability aligns with attack patterns documented in the MITRE ATT&CK framework under the T1566 technique for credential access through phishing and T1041 for data exfiltration. This represents a fundamental failure in the certificate validation process that undermines the core security guarantees provided by SSL/TLS protocols.
The technical nature of this vulnerability can be categorized under CWE-295, which addresses improper certificate validation in security protocols. The flaw demonstrates a classic case of insufficient certificate chain validation where the browser fails to properly verify certificate authorities, certificate expiration dates, and certificate subject names against the target server. This validation failure creates a trust relationship that can be easily manipulated by attackers who can generate or obtain certificates that appear legitimate to the vulnerable browser. The vulnerability also exposes weaknesses in the certificate revocation checking mechanisms that should have been implemented to prevent such attacks.
Mitigation strategies for CVE-2000-0406 require immediate software updates to patched versions of Netscape Communicator and Navigator. Organizations should implement certificate pinning techniques where possible and establish robust monitoring for unusual SSL connection patterns. Network administrators should deploy SSL inspection tools to detect and prevent certificate manipulation attempts. The vulnerability highlights the importance of maintaining up-to-date security software and implementing layered defense mechanisms. Security professionals should also consider implementing additional authentication measures such as multi-factor authentication to reduce the impact of potential certificate compromise. This vulnerability serves as a historical example of how inadequate cryptographic implementation can create severe security risks, emphasizing the critical need for proper certificate validation protocols in all security software implementations.