CVE-2015-2323 in FortiOS
Summary
by MITRE
FortiOS 5.0.x before 5.0.12 and 5.2.x before 5.2.4 supports anonymous, export, RC4, and possibly other weak ciphers when using TLS to connect to FortiGuard servers, which allows man-in-the-middle attackers to spoof TLS content by modifying packets.
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Analysis
by VulDB Data Team • 06/07/2022
The vulnerability identified as CVE-2015-2323 affects FortiOS versions 5.0.x prior to 5.0.12 and 5.2.x prior to 5.2.4, specifically impacting the secure communication protocols used when connecting to FortiGuard servers. This weakness stems from the implementation of TLS connections that permit the use of deprecated and cryptographically weak cipher suites including anonymous, export, and RC4 algorithms. The configuration allows these insecure ciphers to be negotiated during the TLS handshake process, creating a significant security risk that undermines the integrity of encrypted communications between FortiOS devices and FortiGuard services.
The technical flaw represents a failure in cryptographic protocol implementation and security configuration management, aligning with CWE-327 which addresses the use of weak cryptographic algorithms. When these weak ciphers are enabled, attackers can exploit the vulnerability through man-in-the-middle attacks by intercepting and modifying network traffic. The specific cipher suites mentioned such as RC4 are known to have fundamental cryptographic weaknesses that make them susceptible to various attack vectors including key recovery and plaintext prediction. The anonymous cipher suites allow connections without proper authentication, while export ciphers limit key lengths to values that can be easily broken using modern computational resources.
The operational impact of this vulnerability is substantial as it allows attackers to compromise the security of communications between FortiOS devices and FortiGuard services, potentially enabling data interception, modification, and impersonation attacks. This affects organizations using FortiOS for network security management, as the compromise of these connections could lead to unauthorized access to security updates, threat intelligence feeds, and other critical operational data. The vulnerability particularly impacts organizations that rely on FortiGuard services for threat detection, malware signatures, and security policy updates, as attackers could potentially inject malicious content or disrupt legitimate communications.
Organizations should immediately implement mitigations including upgrading to FortiOS versions 5.0.12 or 5.2.4 and later, which contain fixes for the weak cipher suite support. Security administrators must also configure TLS settings to disable weak cipher suites and enforce the use of strong cryptographic algorithms such as those supporting AES-GCM or ChaCha20-Poly1305. The configuration should align with industry best practices and standards including those outlined in NIST SP 800-52 for TLS implementation and the OWASP Top Ten for secure communication protocols. Additionally, network monitoring should be enhanced to detect unusual traffic patterns that might indicate exploitation attempts, and security teams should implement proper key management practices to prevent unauthorized access to cryptographic materials. This vulnerability demonstrates the critical importance of maintaining up-to-date cryptographic implementations and proper security configuration management as outlined in the MITRE ATT&CK framework's defense evasion and credential access tactics.