CVE-2002-1407 in TinySSL
Summary
by MITRE
TinySSL 1.02 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 • 06/13/2018
The vulnerability identified as CVE-2002-1407 affects TinySSL version 1.02 and earlier implementations, representing a critical flaw in certificate validation mechanisms that undermines the fundamental security assurances provided by public key infrastructure. This issue stems from the software's failure to properly enforce basic constraints within X.509 certificates, specifically neglecting to validate the basicConstraints extension that determines whether a certificate can serve as a certificate authority. The absence of this validation creates a significant gap in the certificate chain validation process that malicious actors can exploit to compromise secure communications.
The technical flaw manifests in the improper certificate validation logic where TinySSL fails to check the basicConstraints extension field within intermediate certificates issued by certificate authorities. This extension is crucial as it explicitly defines whether a certificate is permitted to sign other certificates, thereby acting as a certificate authority. When this constraint is not verified, the system accepts intermediate certificates that should not be trusted for signing purposes, creating a pathway for attackers to forge certificates that appear legitimate to the vulnerable software. The vulnerability operates at the core of trust validation mechanisms, where the software essentially accepts any certificate without proper hierarchical validation, making it susceptible to certificate forgery attacks.
The operational impact of this vulnerability is severe and directly enables man-in-the-middle attacks that can compromise the integrity of secure communications. Attackers can exploit this weakness by presenting forged intermediate certificates that appear to be issued by trusted certificate authorities, allowing them to intercept and potentially modify encrypted communications between clients and servers. This capability undermines the entire premise of public key cryptography and digital certificates, as users and applications cannot rely on the certificate validation process to ensure the authenticity of the entities they are communicating with. The vulnerability particularly affects web browsing, email security, and any application that depends on SSL/TLS certificate validation for establishing secure connections.
The security implications extend beyond simple certificate forgery to encompass broader trust model breaches that can lead to complete compromise of secure communication channels. This vulnerability aligns with CWE-295 which addresses improper certificate validation and relates to the broader category of trust management failures in cryptographic systems. From an attack perspective, this vulnerability maps to ATT&CK technique T1552.001 which involves the exploitation of weak or missing certificate validation to establish unauthorized secure connections. Organizations using affected TinySSL implementations face significant risk of data interception, credential theft, and service disruption as attackers can seamlessly impersonate legitimate websites and services.
Mitigation strategies for this vulnerability require immediate software updates to versions that properly implement certificate validation, specifically ensuring that basicConstraints are checked during certificate chain validation. System administrators should also implement additional monitoring and alerting mechanisms to detect unusual certificate validation behavior or attempts to establish connections with certificates that should not be trusted. The remediation process involves not only updating the TinySSL library but also reviewing and strengthening certificate management policies, including implementing certificate pinning where appropriate and ensuring that all certificate validation processes properly enforce the basicConstraints extension. Organizations should conduct thorough vulnerability assessments to identify all systems using affected software versions and implement comprehensive testing to verify that certificate validation now properly enforces certificate authority constraints.