CVE-2001-1499 in VPN-1
Summary
by MITRE
Check Point VPN-1 4.1SP4 using SecuRemote returns different error messages for valid and invalid users, with prompts that vary depending on the authentication method being used, which makes it easier for remote attackers to conduct brute force attacks.
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Analysis
by VulDB Data Team • 06/04/2018
The vulnerability described in CVE-2001-1499 affects Check Point VPN-1 4.1SP4 when configured with SecuRemote functionality, presenting a significant security weakness that directly impacts authentication security. This issue stems from the software's inconsistent error messaging behavior during the authentication process, where the system provides different responses for legitimate versus invalid user accounts. The vulnerability operates at the authentication layer of the VPN infrastructure, specifically within the SecuRemote component that manages remote access connections. The inconsistent error handling creates a predictable pattern that attackers can exploit to determine valid user accounts through systematic trial and error attempts.
The technical flaw manifests as a timing and response differentiation mechanism that reveals information about user account validity to unauthorized parties. When a remote attacker attempts to authenticate, the system's response varies depending on whether the username exists in the system or not, and these variations are further influenced by the specific authentication method being employed. This information disclosure occurs because the system does not implement consistent error handling across all authentication scenarios, allowing attackers to distinguish between valid and invalid usernames through the different error messages returned. The vulnerability directly relates to CWE-200, which covers information exposure, and CWE-305, which addresses authentication bypass through multiple attempts.
The operational impact of this vulnerability extends beyond simple account enumeration, as it enables brute force attacks that can systematically test password combinations against known valid usernames. Attackers can leverage the system's inconsistent error responses to build lists of valid users, then focus their efforts on cracking passwords for those specific accounts rather than conducting random brute force attempts. This significantly reduces the time and computational resources required to compromise user accounts, making the attack surface much more exploitable. The vulnerability affects the availability and confidentiality aspects of the VPN system, as it allows unauthorized access to network resources while potentially exposing sensitive user account information.
Security professionals should consider implementing account lockout mechanisms and rate limiting to prevent automated brute force attacks from exploiting this weakness. The recommended mitigations include configuring the system to return consistent error messages regardless of whether the username exists, implementing account lockout policies after a certain number of failed authentication attempts, and deploying intrusion detection systems to monitor for unusual authentication patterns. Organizations should also consider upgrading to newer versions of Check Point VPN-1 that address this vulnerability and implement proper authentication hardening measures. The ATT&CK framework categorizes this vulnerability under credential access techniques, specifically targeting the use of brute force methods to gain unauthorized access to systems. Additionally, network segmentation and multi-factor authentication implementations can help reduce the overall risk associated with this authentication weakness, as attackers would need additional credentials or access methods beyond simple username enumeration.