Quick Summary
LDAP Anonymous Bind Allowed is a directory service misconfiguration where the LDAP server permits unauthenticated users to bind and query directory information without valid credentials. This may allow attackers to enumerate users, groups, email addresses, and other sensitive directory attributes, increasing reconnaissance capability and facilitating further attacks.
Vulnerability Classification
| Field | Value |
|---|---|
| Vulnerability Type | LDAP Access Control Misconfiguration |
| CWE ID | CWE-284 – Improper Access Control |
| CVE ID | N/A (Configuration Issue) |
| CVSS 4.0 Base Score | 7.4 (High) |
| CVSS Vector | AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:L/VA:N |
| OWASP Category | A05:2021 – Security Misconfiguration |
| Attack Surface | Internal / External Network |
Affected Asset / Environment
- Service: LDAP
- Default Ports: 389 (LDAP), 636 (LDAPS)
- Common Platforms: Active Directory, OpenLDAP
- Testing Method: Black-box / Internal Assessment
- Tools Used: Nmap, ldapsearch
Description
The assessor observed that the LDAP service running on the target server allows anonymous bind operations. During testing, it was possible to establish an LDAP session without providing valid authentication credentials.
Anonymous bind enables unauthenticated users to query directory information. In environments such as Active Directory, this may expose usernames, group memberships, email addresses, and other directory attributes.
While anonymous bind does not directly grant administrative access, it significantly assists attackers in reconnaissance, credential-based attacks, and privilege escalation attempts.
Root Cause
The issue occurs due to improper LDAP configuration where anonymous bind is enabled.
Common root causes include:
- Default directory service configuration left unchanged
- Anonymous access not restricted in LDAP policies
- Lack of directory hardening
- Misconfigured access control lists (ACLs)
Business Impact
Exploitation of this vulnerability may allow attackers to gather detailed information about organizational users and structure. This information may be used for password spraying, phishing campaigns, targeted attacks, or lateral movement.
In regulated environments, exposure of directory data may also introduce compliance risks and privacy concerns.
Technical Impact
An attacker can:
- Enumerate user accounts
- Identify group memberships
- Retrieve email addresses
- Extract domain structure information
- Map organizational hierarchy
This information may significantly improve the success rate of subsequent authentication or social engineering attacks.
Proof of Concept (PoC)
Step1: Identify LDAP Service
nmap -sV -p 389 <target-ip>
If port 389 is open and service is identified as LDAP, proceed to bind testing.
Step2: Test Anonymous Bind
ldapsearch -x -h <target-ip> -b "dc=example,dc=com"
If the command returns directory entries without requiring credentials, anonymous bind is enabled.
Step3: Enumerate Directory Information
ldapsearch -x -h <target-ip> -s base namingcontexts
If naming contexts or domain components are returned, information disclosure is confirmed.
Step4: Attempt User Enumeration
ldapsearch -x -h <target-ip> "(objectClass=user)"
If user details are returned without authentication, the vulnerability is validated.
Exploitation Prerequisites
- Network access to port 389 or 636
- LDAP service enabled
- Anonymous bind permitted
- No access restriction policies enforced
Remediation
It is recommended that anonymous LDAP bind be disabled.
Recommended actions:
- Configure LDAP to require authentication for bind operations
- Restrict directory queries to authorized users only
- Harden LDAP access control lists
- Enforce LDAPS with encryption
- Restrict LDAP service access via firewall rules
- Regularly audit directory permissions
Detection and Monitoring
- Monitor LDAP bind attempts in directory logs
- Alert on repeated unauthenticated bind attempts
- Conduct periodic LDAP configuration audits
- Restrict directory enumeration via security policy