CVE-2016-3125 in ProFTPD
Summary
by MITRE
The mod_tls module in ProFTPD before 1.3.5b and 1.3.6 before 1.3.6rc2 does not properly handle the TLSDHParamFile directive, which might cause a weaker than intended Diffie-Hellman (DH) key to be used and consequently allow attackers to have unspecified impact via unknown vectors.
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Analysis
by VulDB Data Team • 10/09/2024
The vulnerability identified as CVE-2016-3125 affects the mod_tls module within ProFTPD software versions prior to 1.3.5b and 1.3.6rc2, representing a critical cryptographic weakness that undermines the security of secure file transfer operations. This flaw specifically targets the TLSDHParamFile directive implementation, which governs the Diffie-Hellman parameter configuration for TLS connections. The improper handling of this directive results in the potential use of suboptimal Diffie-Hellman keys that significantly weaken the cryptographic strength of the secure communication channel. The vulnerability stems from inadequate validation and processing of Diffie-Hellman parameters, allowing attackers to potentially exploit the reduced key strength to compromise the security of encrypted file transfers. This weakness directly relates to CWE-326, which addresses the use of weak cryptographic algorithms and improper key management in security implementations.
The technical flaw manifests when the mod_tls module fails to properly validate or enforce the cryptographic strength of Diffie-Hellman parameters specified through the TLSDHParamFile directive. This allows for the possibility of using weak DH parameters that can be more easily broken through computational attacks, particularly those utilizing specialized algorithms like the small subgroup confinement attack or the general number field sieve. The operational impact of this vulnerability extends beyond simple credential interception, as it compromises the fundamental cryptographic integrity of the TLS handshake process. Attackers who can exploit this weakness may be able to perform man-in-the-middle attacks, decrypt intercepted traffic, or potentially gain unauthorized access to sensitive data transferred through the vulnerable FTP service. The unspecified impact vector suggests that the vulnerability could enable various attack scenarios depending on the specific implementation details and network conditions.
The security implications of CVE-2016-3125 align with ATT&CK technique T1566, which covers social engineering attacks, and more specifically relates to the compromise of secure communication channels through cryptographic weaknesses. Organizations running vulnerable ProFTPD instances face significant risk of data breaches, as the weakened cryptographic parameters make it easier for adversaries to intercept and decrypt sensitive file transfers. The vulnerability particularly affects environments where secure file transfer is critical, such as financial institutions, healthcare organizations, and government agencies that rely on FTP services for data exchange. The impact is further compounded by the fact that the weakness is not immediately apparent during normal operation, making detection and remediation challenging. Security professionals should consider this vulnerability in the context of broader cryptographic hygiene practices and ensure that all TLS implementations properly enforce strong Diffie-Hellman parameter requirements.
Organizations should immediately implement mitigation strategies including upgrading to ProFTPD versions 1.3.5b or 1.3.6rc2 and higher, which contain the necessary patches to address the TLSDHParamFile directive handling. Additionally, system administrators should verify that all Diffie-Hellman parameters used in their TLS configurations meet current cryptographic strength requirements, typically requiring at least 2048-bit keys for adequate security. The vulnerability demonstrates the critical importance of proper cryptographic parameter management and highlights the need for regular security assessments of TLS implementations. Security monitoring should include checks for weak cryptographic parameters and proper validation of TLS configuration directives. Furthermore, organizations should consider implementing additional security controls such as certificate pinning and enhanced network monitoring to detect potential exploitation attempts. The remediation process should also include comprehensive testing of the updated configurations to ensure that the cryptographic strength has been properly restored without disrupting legitimate file transfer operations.