CVE-2002-0970 in KDE
Summary
by MITRE
The SSL capability for Konqueror in KDE 3.0.2 and earlier does not verify the Basic Constraints for an intermediate CA-signed certificate, which allows remote attackers to spoof the certificates of trusted sites via a man-in-the-middle attack.
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Analysis
by VulDB Data Team • 09/06/2025
The vulnerability described in CVE-2002-0970 represents a critical flaw in the SSL certificate validation implementation within Konqueror web browser, which was part of the KDE 3.0.2 desktop environment. This security weakness specifically targets the certificate chain validation process where the browser fails to properly enforce the Basic Constraints extension within intermediate CA certificates. The Basic Constraints extension is a fundamental component of x509 certificate structure that defines whether a certificate can function as a certificate authority and specifies the maximum depth of valid certification paths. When this validation is bypassed, attackers can exploit the gap in certificate verification to construct fraudulent certificates that appear legitimate to the browser.
The technical nature of this vulnerability stems from the incomplete implementation of certificate chain validation within Konqueror's SSL stack. In proper SSL/TLS certificate validation, when a certificate is presented by a server, the client must traverse the certificate chain back to a trusted root CA while enforcing all relevant certificate extensions including Basic Constraints. The Basic Constraints extension contains two key fields: ca boolean indicating if the certificate can act as a CA, and pathlen integer specifying the maximum number of intermediate certificates that can exist between this certificate and a terminal certificate. When Konqueror fails to verify these constraints for intermediate certificates, it allows attackers to create a certificate chain where an intermediate CA certificate incorrectly claims to be a CA when it should not be permitted to issue certificates.
This vulnerability creates a significant operational risk for users browsing the internet through affected versions of Konqueror, as it enables sophisticated man-in-the-middle attacks that can completely bypass the browser's security mechanisms. Attackers can leverage this weakness to impersonate legitimate websites by presenting forged certificates that pass the browser's validation checks, potentially leading to credential theft, data interception, and complete session hijacking. The impact extends beyond simple web browsing as users may unknowingly submit sensitive information to attackers who have successfully spoofed trusted sites. This vulnerability directly violates the fundamental security principle of certificate-based authentication and undermines the trust model that SSL/TLS protocols are designed to establish. The flaw represents a failure in the certificate validation logic that should be implemented according to standards such as rfc5280 and the x509 v3 certificate specification.
From a cybersecurity perspective, this vulnerability aligns with attack patterns documented in the attack tree framework and can be categorized under the MITRE ATT&CK framework's initial access and credential access techniques. Specifically, it relates to techniques involving network sniffing and man-in-the-middle attacks where attackers compromise the authenticity of communications. The vulnerability also connects to CWE-310, which addresses cryptographic weaknesses in certificate validation, and CWE-295, which covers improper certificate validation. Organizations using affected KDE versions would be particularly vulnerable in environments where users access sensitive resources through Konqueror, as the attack vector could be exploited through various network interception methods including wireless network attacks, compromised network infrastructure, or DNS spoofing attacks that redirect traffic to malicious servers.
The recommended mitigations for this vulnerability involve immediate upgrading to Konqueror versions that properly implement certificate validation including Basic Constraints checking. System administrators should also consider implementing additional security measures such as certificate pinning for critical sites, network monitoring to detect unusual certificate validation patterns, and user education about recognizing potential security warnings. The broader lesson from this vulnerability emphasizes the critical importance of comprehensive certificate validation in all SSL/TLS implementations and highlights the need for thorough security testing of cryptographic components. Organizations should also implement automated vulnerability scanning to detect similar issues in other browser implementations and ensure that all certificate validation processes strictly adhere to established cryptographic standards and best practices.