CVE-2006-6981 in 3proxy
Summary
by MITRE
3proxy 0.5 to 0.5.2, when NT-encoded passwords are being used, allows remote attackers to cause a denial of service (blocked account) via unspecified vectors related to NTLM authentication, which causes a password hash to be overwritten.
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Analysis
by VulDB Data Team • 08/19/2018
The vulnerability identified as CVE-2006-6981 affects 3proxy versions 0.5 through 0.5.2 and represents a significant security flaw in the NTLM authentication mechanism. This issue specifically manifests when NT-encoded passwords are utilized within the proxy server environment, creating a condition where remote attackers can exploit the system to trigger a denial of service scenario. The vulnerability operates through an authentication-related vector that fundamentally compromises the integrity of password handling within the proxy infrastructure.
The technical flaw stems from improper handling of NTLM authentication sequences where password hash values become overwritten during the authentication process. When NT-encoded passwords are processed, the system fails to maintain proper state management for hash values, allowing malicious actors to manipulate the authentication flow in such a way that legitimate user accounts become blocked. This overwrite mechanism effectively prevents authorized users from accessing the proxy services while simultaneously creating a persistent denial of service condition that can persist until manual intervention occurs.
The operational impact of this vulnerability extends beyond simple service disruption as it creates a persistent security threat that can be exploited repeatedly by attackers. The blocking of legitimate accounts represents a critical compromise of system availability and user access control, potentially affecting multiple users simultaneously if the vulnerability is exploited at scale. Organizations relying on 3proxy for network access control and authentication may experience cascading failures in their proxy infrastructure, particularly in environments where authentication is critical for network segmentation and access management.
This vulnerability aligns with CWE-254 and CWE-311 categories, specifically addressing weaknesses in authentication mechanisms and insufficient cryptographic protection. The flaw demonstrates characteristics consistent with attack patterns documented in the ATT&CK framework under T1110.003 for credential access and T1499.004 for network denial of service. The vulnerability exploits a fundamental flaw in the NTLM implementation that allows attackers to manipulate authentication state, effectively creating a persistent access control issue that requires system-level intervention to resolve.
Mitigation strategies should focus on immediate version upgrades to 3proxy 0.5.3 or later, which contain the necessary patches to address the NTLM authentication handling. Organizations should implement network segmentation to limit exposure of vulnerable proxy servers and consider disabling NTLM authentication where possible. Additionally, monitoring systems should be enhanced to detect unusual authentication patterns that may indicate exploitation attempts. The recommended approach includes conducting comprehensive vulnerability assessments of all proxy infrastructure, implementing proper access controls, and establishing incident response procedures specifically tailored to address authentication-based denial of service scenarios. Regular security updates and patch management processes should be enforced to prevent similar vulnerabilities from manifesting in other components of the network infrastructure.