CVE-2020-17477 in UCS@school
Summary
by MITRE • 10/26/2023
Incorrect LDAP ACLs in ucs-school-ldap-acls-master in UCS@school before 4.4v5-errata allow remote teachers, staff, and school administrators to read LDAP password hashes (sambaNTPassword, krb5Key, sambaPasswordHistory, and pwhistory) via LDAP search requests. For example, a teacher can gain administrator access via an NTLM hash.
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Analysis
by VulDB Data Team • 11/18/2023
This vulnerability resides within the ucs-school-ldap-acls-master component of the UCS@school platform, a widely deployed educational management system that provides integrated identity and access management solutions for schools. The flaw represents a critical misconfiguration in the Lightweight Directory Access Protocol access control mechanisms that govern how different user roles can interact with the directory service. The vulnerability affects versions prior to 4.4v5-errata, indicating that this was a known issue that required specific patching to resolve the underlying access control problems. The root cause lies in improper implementation of access control lists that fail to adequately restrict read permissions for sensitive password-related attributes within the LDAP directory structure.
The technical exploitation of this vulnerability occurs through LDAP search operations that target specific password hash attributes including sambaNTPassword, krb5Key, sambaPasswordHistory, and pwhistory. These attributes contain critical authentication data that should remain strictly protected from unauthorized access. Attackers with credentials from lower-privilege roles such as teachers, staff members, or school administrators can leverage this misconfiguration to perform LDAP queries that return these password hash values. The implications are severe because the sambaNTPassword attribute specifically contains NTLM hash information that can be used for pass-the-hash attacks, allowing an attacker to escalate privileges and gain administrative access to the system. This represents a classic privilege escalation vulnerability where lower-privileged users can obtain elevated credentials through improper access controls.
The operational impact of this vulnerability extends beyond simple credential theft, as it fundamentally compromises the security model of the entire educational management platform. When teachers or staff members can access administrator password hashes, it creates a complete breakdown in the principle of least privilege that should govern any secure system. The ability to perform pass-the-hash attacks through NTLM hashes means that attackers can bypass traditional authentication mechanisms and gain unauthorized access to critical system resources, user accounts, and potentially the entire network infrastructure managed by the UCS@school platform. This vulnerability undermines the trust model that educational institutions rely upon for protecting student data and maintaining secure computing environments, potentially exposing sensitive information including personal student records, academic data, and institutional resources.
Organizations affected by this vulnerability should immediately implement the patch released in UCS@school 4.4v5-errata to correct the LDAP ACL misconfigurations. Network segmentation and monitoring should be enhanced to detect unusual LDAP search patterns that might indicate exploitation attempts. Security audits should verify that all LDAP access controls are properly configured and that no unauthorized read permissions exist for password hash attributes. The vulnerability aligns with CWE-284 Access Control Issues, specifically targeting improper access control mechanisms in directory services, and represents a significant concern under ATT&CK tactic TA0006 Credential Access where adversaries seek to obtain credentials through various means including exploitation of weak access controls. Regular security assessments of directory service configurations should be conducted to prevent similar misconfigurations that could provide unauthorized access to sensitive authentication data.