CVE-2026-15041 in 389 Directory Server
Summary
by MITRE • 07/08/2026
A flaw was found in 389 Directory Server. The PBKDF2-SHA256 password verification function uses standard memcmp() for comparing password hashes instead of a constant-time comparison function. A remote attacker could potentially use timing measurements of LDAP bind attempts to infer partial hash information, though practical exploitation is extremely difficult due to PBKDF2 computational overhead.
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Analysis
by VulDB Data Team • 07/08/2026
The vulnerability exists within the 389 Directory Server authentication mechanism where the PBKDF2-SHA256 password verification process employs a non-constant-time comparison function. This flaw stems from the use of standard memcmp() operations during hash validation rather than implementing proper constant-time comparison algorithms. The issue creates a timing side-channel attack vector that allows adversaries to potentially extract partial information about password hashes through careful analysis of response times during LDAP bind operations. According to CWE-203, this represents a timing attack vulnerability where the attacker can infer sensitive information based on the time taken to perform comparisons.
The technical implementation flaw lies in how the server handles password verification when processing LDAP bind requests. During authentication, when comparing the provided password hash against the stored hash, the system uses memcmp() which returns immediately upon finding the first mismatched byte. This behavior creates measurable differences in execution time that can be exploited by attackers monitoring response patterns. The vulnerability specifically affects the PBKDF2-SHA256 implementation where the computational complexity of PBKDF2 adds additional timing variations that could theoretically be analyzed to deduce partial hash information.
From an operational perspective, while the practical exploitation difficulty is high due to the inherent computational overhead of PBKDF2 which introduces significant processing time variance, the vulnerability still poses a risk in environments where attackers have sufficient access to monitor authentication timing characteristics. The attack requires precise timing measurements across multiple bind attempts and would be challenging to execute successfully against systems with proper network security controls and monitoring. However, in less protected environments or when combined with other reconnaissance techniques, this timing side-channel could potentially aid in password cracking efforts.
Mitigation strategies should focus on implementing constant-time comparison functions throughout the authentication process to eliminate timing variations that could leak information about hash values. Organizations should update their 389 Directory Server installations to versions containing patched implementations of cryptographic comparisons and consider deploying additional monitoring controls to detect unusual authentication timing patterns. The ATT&CK framework categorizes this as a credential access technique under T1110.002, specifically targeting credential dumping through timing attacks. Network administrators should also implement rate limiting and account lockout mechanisms to reduce the effectiveness of any potential exploitation attempts while maintaining system availability for legitimate users.