CVE-2017-6339 in InterScan Web Security Virtual Appliance
Summary
by MITRE
Trend Micro InterScan Web Security Virtual Appliance (IWSVA) 6.5 before CP 1746 mismanages certain key and certificate data. Per IWSVA documentation, by default, IWSVA acts as a private Certificate Authority (CA) and dynamically generates digital certificates that are sent to client browsers to complete a secure passage for HTTPS connections. It also allows administrators to upload their own certificates signed by a root CA. An attacker with low privileges can download the current CA certificate and Private Key (either the default ones or ones uploaded by administrators) and use those to decrypt HTTPS traffic, thus compromising confidentiality. Also, the default Private Key on this appliance is encrypted with a very weak passphrase. If an appliance uses the default Certificate and Private Key provided by Trend Micro, an attacker can simply download these and decrypt the Private Key using the default/weak passphrase.
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Analysis
by VulDB Data Team • 09/24/2024
The vulnerability identified as CVE-2017-6339 affects Trend Micro InterScan Web Security Virtual Appliance version 6.5 before CP 1746, representing a critical weakness in the appliance's certificate management and cryptographic security implementation. This vulnerability stems from improper handling of cryptographic key and certificate data within the web security appliance, which fundamentally undermines the security of HTTPS traffic inspection and encryption. The appliance operates as a private Certificate Authority by default, dynamically generating digital certificates to facilitate secure HTTPS connections between clients and servers, a mechanism commonly referred to as SSL/TLS interception or man-in-the-middle inspection. This design requires the appliance to possess valid certificates and corresponding private keys that can decrypt and re-encrypt HTTPS traffic, making the security of these cryptographic materials paramount to overall system integrity.
The technical flaw manifests in two primary weaknesses that compound to create an exploitable scenario for attackers with minimal privileges. First, the appliance allows unauthorized users to download the current CA certificate and private key through standard administrative interfaces, bypassing proper access controls and privilege enforcement mechanisms. This represents a clear violation of the principle of least privilege and demonstrates inadequate session management and authentication controls. Second, when administrators utilize the default certificate and private key provided by Trend Micro, the private key is encrypted with a weak passphrase that can be easily cracked through brute force or dictionary attacks. This weakness directly relates to CWE-326, which addresses inadequate encryption strength, and CWE-310, which covers cryptographic weaknesses in key management. The combination of these vulnerabilities creates a path for attackers to compromise the entire HTTPS interception mechanism and gain access to decrypted traffic data.
The operational impact of this vulnerability extends beyond simple privilege escalation to encompass complete compromise of the web security appliance's core functionality and the confidentiality of all intercepted traffic. An attacker who successfully exploits this vulnerability can decrypt all HTTPS communications passing through the appliance, potentially accessing sensitive data including login credentials, personal information, financial transactions, and corporate communications. This compromise directly affects the appliance's ability to provide security services as intended, undermining the trust model that organizations place in web security solutions. The vulnerability also impacts the broader security infrastructure since the compromised private key can be used to forge certificates for any domain, enabling widespread impersonation attacks and bypassing certificate pinning mechanisms that security-conscious organizations might have implemented. This represents a significant concern from an attacker's perspective as outlined in the MITRE ATT&CK framework under techniques related to credential access and privilege escalation through compromised certificates.
Mitigation strategies for this vulnerability require immediate action to address both the access control and cryptographic weaknesses. Organizations should first update their IWSVA appliances to version 6.5 CP 1746 or later, which includes patches addressing the certificate download and key management issues. Administrators must immediately regenerate and replace any default certificates and private keys with strong, randomly generated cryptographic materials using appropriate key lengths and encryption algorithms. The private keys should be protected with strong passphrases that meet current cryptographic standards, typically requiring at least 12 characters with mixed character sets and avoiding dictionary words or common patterns. Network segmentation and monitoring should be implemented to detect unauthorized access attempts to certificate management interfaces, while access controls should be strictly enforced to limit certificate download privileges to authorized administrators only. Additionally, organizations should implement certificate lifecycle management processes that include regular key rotation and proper key storage mechanisms to prevent future occurrences of similar vulnerabilities. The remediation process should also include comprehensive security auditing to ensure no unauthorized certificate downloads or key compromises have occurred during the vulnerable period, as this vulnerability directly relates to CWE-312, which addresses exposure of sensitive data through improper handling of cryptographic materials.