CVE-2024-5953 is a denial of service (DoS) vulnerability identified in the 389-ds-base LDAP server, a widely used open-source directory server implementation. The flaw arises from improper validation of consistency within input, specifically related to password hashes during login attempts. An authenticated user can exploit this vulnerability by attempting to authenticate with a user account that contains a malformed password hash. This malformed input triggers a failure in the server’s processing logic, causing the LDAP server to crash or become unresponsive, resulting in denial of service. The vulnerability does not expose any confidential data nor does it allow modification of data, but it impacts the availability of the LDAP service, which is critical for authentication and directory services in many enterprise environments. The CVSS 3.1 base score of 5.7 reflects that the attack vector is adjacent network (AV:A), requires low attack complexity (AC:L), and privileges (PR:L) but no user interaction (UI:N). The scope is unchanged (S:U), and the impact is limited to availability (A:H) with no confidentiality or integrity impact. No known exploits have been reported in the wild as of the publication date. The vulnerability was assigned and published by Red Hat, indicating it affects Red Hat’s distribution of 389 Directory Server, but other distributions using the same codebase may also be vulnerable. The lack of patch links suggests that fixes may be pending or available through vendor advisories.

For European organizations, the primary impact is disruption of LDAP authentication services, which can halt access to critical applications and systems relying on centralized directory services. This can affect user productivity, delay business operations, and potentially cause cascading failures in dependent systems. Organizations in sectors with high reliance on LDAP for identity management—such as government, finance, healthcare, and telecommunications—may experience significant operational impact. Since the attack requires authentication, insider threats or compromised credentials could be leveraged to trigger the DoS. The availability impact could also be exploited as part of a broader attack to cause service outages or to distract security teams. However, the lack of confidentiality or integrity impact limits the risk of data breaches or unauthorized data modification. The medium severity rating suggests that while the threat is serious, it is not critical, but still warrants timely remediation to maintain service continuity.

European organizations should first verify if they are running vulnerable versions of the 389-ds-base LDAP server, particularly Red Hat distributions or other Linux variants using this software. Immediate mitigation includes applying vendor patches or updates once available. In the absence of patches, organizations can implement strict monitoring of LDAP authentication logs to detect anomalous login attempts involving malformed password hashes. Limiting the number of failed login attempts and enforcing strong password policies can reduce the risk of exploitation. Network segmentation and access controls should restrict LDAP server access to trusted internal networks and authenticated users only. Additionally, deploying rate limiting or connection throttling on LDAP servers can help mitigate DoS attempts. Regular backups and failover configurations for directory services can minimize downtime in case of an attack. Finally, educating administrators about this vulnerability and ensuring incident response plans include LDAP service disruptions will improve preparedness.