CVE-2013-0243 in haskell-tls-extra
Summary
by MITRE
haskell-tls-extra before 0.6.1 has Basic Constraints attribute vulnerability may lead to Man in the Middle attacks on TLS connections
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Analysis
by VulDB Data Team • 03/07/2024
The vulnerability identified as CVE-2013-0243 affects the haskell-tls-extra library version 0.6.1 and earlier, presenting a critical security flaw in the handling of X.509 certificate Basic Constraints attributes. This library serves as an extension to the tls package in Haskell, providing additional functionality for secure communication through Transport Layer Security protocols. The flaw specifically manifests in how the library processes certificate chains, particularly when validating the basicConstraints extension that determines whether a certificate is a CA certificate and whether it can issue subordinate certificates. The Basic Constraints attribute is a fundamental component of PKI infrastructure, defining the hierarchical structure of trust relationships between certificate authorities and their issued certificates.
The technical implementation flaw stems from insufficient validation of the basicConstraints extension within the certificate verification process. When a certificate chain is processed, the library fails to properly enforce the constraints defined in the Basic Constraints extension, allowing certificates that should not act as certificate authorities to be treated as such during the validation process. This weakness creates a scenario where an attacker could potentially construct a malicious certificate chain that bypasses normal certificate validation procedures. The vulnerability is particularly dangerous because it operates at the core of TLS certificate validation, where trust decisions are made. According to CWE-311, this represents a weakness in the handling of cryptographic data, specifically in the validation of certificate attributes that are critical for establishing secure communication channels. The flaw enables attackers to exploit the trust model by presenting certificates that appear valid but violate fundamental PKI principles.
The operational impact of this vulnerability is severe and directly enables man-in-the-middle attacks against TLS connections that utilize the affected haskell-tls-extra library. An attacker who can influence the certificate chain presented during TLS handshakes can exploit this weakness to present fraudulent certificates that will be accepted by vulnerable applications. This compromises the integrity of the TLS protocol by allowing the attacker to impersonate legitimate services or intercept communications between clients and servers. The vulnerability affects any application using the haskell-tls-extra library for TLS connections, including web servers, email servers, and other network services that rely on secure communication protocols. The attack surface is particularly broad since the library is used in various Haskell-based applications and systems where secure TLS communication is required. From an ATT&CK framework perspective, this vulnerability maps to T1573.001 (TLS Spoofing) and T1592.004 (Resource Hijacking), as it enables attackers to manipulate the secure communication channel and potentially gain unauthorized access to sensitive data.
The remediation strategy involves upgrading to haskell-tls-extra version 0.6.1 or later, which contains the necessary fixes for proper Basic Constraints validation. Organizations should conduct thorough vulnerability assessments to identify all systems using the affected library and implement patch management procedures to ensure timely updates. Additionally, security monitoring should be enhanced to detect potential exploitation attempts, including unusual certificate validation patterns or certificate chain anomalies. System administrators should also consider implementing certificate pinning mechanisms as an additional defense-in-depth measure, though this approach has its own limitations and complexity considerations. The fix addresses the core validation logic by implementing proper enforcement of the basicConstraints extension, ensuring that certificates without the appropriate CA flag cannot be used to validate other certificates in the chain. This aligns with security best practices outlined in RFC 5280 and the broader PKI security framework that governs certificate validation procedures and trust relationships in secure communications. Organizations should also review their certificate management policies and ensure proper certificate lifecycle management to prevent similar issues in other components of their security infrastructure.