LDAP Injector

LDAP injection is a critical web application vulnerability that targets systems using the Lightweight Directory Access Protocol for authentication and data retrieval. Similar in concept to SQL injection, LDAP injection occurs when user-supplied input is incorporated into LDAP queries without proper sanitization, allowing attackers to modify the query logic and bypass authentication or extract unauthorized information from directory services.

What Is LDAP and Why Is It Targeted?

LDAP is a protocol used to access and manage directory information services, most commonly Microsoft Active Directory. Organizations use LDAP for centralized authentication, employee directories, email address books, and access control management. Because LDAP often serves as the authentication backbone for corporate networks, an LDAP injection vulnerability can provide attackers with broad access to enterprise systems and sensitive employee data.

How LDAP Injection Attacks Work

LDAP queries use a specific filter syntax to search directory entries. A typical authentication query might look like (&(uid=username)(password=secret)). When an application constructs this query by directly concatenating user input, an attacker can inject special characters - particularly parentheses, ampersands, pipes, and asterisks - to alter the query logic. By injecting *)(uid=*))(|(uid=* or similar payloads, attackers can bypass password checks, enumerate directory entries, or extract attribute values.

Common LDAP Injection Scenarios

The most frequently exploited scenario involves authentication bypass, where injected characters cause the LDAP query to return a valid result regardless of the provided password. Other attack scenarios include data exfiltration through blind LDAP injection (inferring information from application responses), enumeration of user accounts and group memberships, and discovery of internal network structure through directory traversal. These attacks are particularly dangerous in enterprise environments where LDAP controls access to multiple interconnected systems.

Prevention and Mitigation

Defending against LDAP injection requires input validation and proper escaping of special LDAP characters before incorporating user input into queries. Applications should use parameterized LDAP queries where available, implement least-privilege access for LDAP service accounts, and deploy monitoring to detect unusual query patterns. Understanding LDAP injection techniques helps security teams identify and remediate these vulnerabilities before attackers exploit them in production environments.