CVE-2017-7551 in 389-ds-base
Summary
by MITRE
389-ds-base version before 1.3.5.19 and 1.3.6.7 are vulnerable to password brute-force attacks during account lockout due to different return codes returned on password attempts.
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Analysis
by VulDB Data Team • 12/16/2022
The vulnerability identified as CVE-2017-7551 affects the 389 Directory Server base software, specifically versions prior to 1.3.5.19 and 1.3.6.7, presenting a significant security weakness in authentication mechanisms. This flaw resides within the directory service's handling of password validation processes, creating an avenue for malicious actors to exploit account lockout functionality through systematic brute-force attempts. The core issue stems from inconsistent return codes that are generated when password authentication fails, allowing attackers to distinguish between different types of authentication failures.
The technical implementation of this vulnerability demonstrates a critical flaw in the server's authentication logic where legitimate password attempts and invalid password attempts return different error codes. This differential response enables an attacker to conduct automated password guessing attacks by monitoring the server's responses to determine whether their guesses are close to the correct password. The inconsistent return codes essentially provide a timing-based side-channel attack vector that undermines the intended security controls designed to prevent unauthorized access through account lockout mechanisms.
From an operational perspective, this vulnerability significantly weakens the directory server's resistance to credential stuffing and password brute-force attacks, particularly when combined with account lockout policies that are meant to protect against such threats. The impact extends beyond simple unauthorized access as it can lead to denial of service conditions when attackers systematically target accounts, causing legitimate users to be locked out while attackers continue their attempts. This vulnerability particularly affects environments where 389-ds-base serves as a central authentication repository for multiple applications and services, amplifying the potential damage from successful exploitation.
The security implications of CVE-2017-7551 align with CWE-305 authentication weaknesses and can be categorized under the ATT&CK technique T1110.003 for Brute Force. Organizations relying on this directory service for authentication purposes face increased risk of credential compromise, especially when combined with other attack vectors that leverage the predictable response patterns. The vulnerability demonstrates a failure in implementing proper authentication error handling that should mask the specific nature of authentication failures to prevent attackers from gaining insights into the authentication process.
Mitigation strategies for this vulnerability require immediate patching to versions 1.3.5.19 or 1.3.6.7, which contain the necessary fixes for consistent error code handling during authentication attempts. Security teams should also implement additional protective measures such as rate limiting for authentication attempts, enhanced monitoring for unusual authentication patterns, and consideration of multi-factor authentication mechanisms. Network-level protections including firewall rules that limit authentication attempts from specific IP addresses and intrusion detection systems configured to identify brute-force attack patterns can provide additional defense layers. The fix implemented in the patched versions ensures that all authentication failures return consistent error codes, eliminating the side-channel information that attackers previously exploited to conduct effective brute-force attacks against locked accounts.