CVE-2016-4984 in openldap-servers
Summary
by MITRE
/usr/libexec/openldap/generate-server-cert.sh in openldap-servers sets weak permissions for the TLS certificate, which allows local users to obtain the TLS certificate by leveraging a race condition between the creation of the certificate, and the chmod to protect it.
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Analysis
by VulDB Data Team • 03/04/2025
The vulnerability identified as CVE-2016-4984 resides within the openldap-servers package, specifically in the /usr/libexec/openldap/generate-server-cert.sh script. This flaw represents a classic race condition vulnerability that exploits the timing gap between certificate generation and permission setting. The issue manifests when the script creates a TLS certificate file without immediately establishing proper file permissions, leaving the certificate temporarily accessible to unauthorized local users. The weakness stems from the script's failure to properly secure the certificate file during its creation process, creating a window of opportunity for privilege escalation attacks.
This vulnerability directly maps to CWE-362, which describes a race condition flaw where two or more processes access shared resources concurrently, leading to inconsistent or insecure states. The technical implementation involves the script executing certificate generation commands followed by chmod operations that are not atomic, creating a temporal gap where the certificate file remains world-readable. Attackers can exploit this by rapidly polling for the certificate file's existence and attempting to read it before the permission changes take effect. The race condition typically occurs within milliseconds, making it particularly challenging to detect and prevent through conventional monitoring approaches.
The operational impact of this vulnerability extends beyond simple information disclosure, as the TLS certificate contains sensitive cryptographic material that could be used to impersonate the LDAP server or decrypt intercepted communications. Local users with minimal privileges can leverage this flaw to obtain certificate files that may contain private keys, enabling man-in-the-middle attacks against LDAP services. The vulnerability affects systems running openldap-servers versions prior to the patched release, potentially compromising the integrity of authentication services that rely on LDAP for user management. This creates a significant risk for organizations where LDAP servers handle sensitive authentication data, as the compromised certificate could be used to establish unauthorized access to critical systems.
Mitigation strategies should focus on immediate patching of affected openldap-servers packages to ensure proper atomic file creation with appropriate permissions. System administrators should also implement monitoring for unauthorized access attempts to certificate files and consider implementing file integrity monitoring solutions to detect changes to sensitive TLS certificate locations. The fix typically involves modifying the certificate generation script to create files with restrictive permissions immediately upon creation, eliminating the race condition window. Additionally, organizations should conduct comprehensive audits of their LDAP server configurations and certificate management practices to identify other potential race conditions or permission-related vulnerabilities. This vulnerability demonstrates the critical importance of proper file permission handling in security-sensitive scripts and aligns with ATT&CK technique T1068, which covers the exploitation of local privilege escalation vulnerabilities through race conditions and weak file permissions.