CVE-2023-0614: Samba Information Disclosure Vulnerability

CVE-2023-0614 Overview

CVE-2023-0614 is an Information Disclosure vulnerability in Samba Active Directory Domain Controller (AD DC) that allows authenticated attackers to obtain confidential attributes, including BitLocker recovery keys, through crafted LDAP filter queries. This vulnerability exists because the original fix for CVE-2018-10919 (Confidential attribute disclosure via LDAP filters) was insufficient, leaving a bypass that enables unauthorized access to sensitive directory information.

Critical Impact

Authenticated attackers can extract BitLocker recovery keys and other confidential attributes from Samba AD DC, potentially compromising encrypted data across the entire organization.

Affected Products

• Samba versions prior to 4.16.10
• Samba versions prior to 4.17.7
• Samba 4.18.0 (including release candidates rc1 through rc4)

Discovery Timeline

• 2023-04-03 - CVE-2023-0614 published to NVD
• 2025-02-13 - Last updated in NVD database

Technical Details for CVE-2023-0614

Vulnerability Analysis

The vulnerability stems from an incomplete fix for CVE-2018-10919, which addressed confidential attribute disclosure through LDAP filters in Samba AD DC deployments. Despite the patches applied in versions 4.6.16, 4.7.9, 4.8.4, and 4.9.7, the mitigation did not comprehensively address all exploitation vectors. This allows attackers with valid credentials to craft LDAP queries that bypass access control mechanisms designed to protect confidential attributes.

The most significant impact involves the potential extraction of BitLocker recovery keys stored in Active Directory. Organizations using Samba as their AD DC and storing BitLocker keys in the directory are particularly vulnerable, as compromised recovery keys could allow attackers to decrypt BitLocker-protected drives across the enterprise.

Root Cause

The root cause is classified under CWE-200 (Exposure of Sensitive Information to an Unauthorized Actor) and CWE-312 (Cleartext Storage of Sensitive Information). The insufficient fix failed to properly restrict LDAP filter operations that could be used to infer or directly retrieve confidential attribute values. The access control implementation did not account for all possible LDAP filter constructions that could be used to enumerate protected data.

Attack Vector

The attack vector is network-based and requires low-privileged authenticated access to the Samba AD DC. An attacker with any valid domain credentials can exploit this vulnerability by:

1. Connecting to the Samba LDAP service with valid domain credentials
2. Constructing LDAP search filters designed to probe confidential attributes
3. Using boolean-based or inference techniques to extract attribute values
4. Targeting high-value attributes such as ms-FVE-RecoveryPassword (BitLocker recovery keys)

The vulnerability requires no user interaction and can be exploited remotely over the network. The attack complexity is low, making it accessible to attackers with basic LDAP query knowledge.

Detection Methods for CVE-2023-0614

Indicators of Compromise

• Unusual LDAP search queries targeting confidential attributes such as ms-FVE-RecoveryPassword or ms-FVE-RecoveryInformation
• High volume of LDAP queries from single authenticated users probing attribute values
• LDAP filter patterns using comparison operators against known confidential attribute names

Detection Strategies

• Enable detailed LDAP query logging on Samba AD DC servers to capture all search operations
• Implement SIEM rules to alert on LDAP queries containing BitLocker-related attribute names
• Monitor for authenticated users making unusual numbers of LDAP search requests
• Deploy network monitoring to identify LDAP traffic patterns consistent with attribute enumeration

Monitoring Recommendations

• Review Samba audit logs regularly for access attempts to confidential attributes
• Establish baseline LDAP query patterns and alert on deviations
• Configure alerts for any access to BitLocker recovery key attributes outside of normal administrative workflows

How to Mitigate CVE-2023-0614

Immediate Actions Required

• Upgrade Samba to the latest patched version (4.16.10, 4.17.7, 4.18.1 or later) immediately
• Audit all BitLocker recovery keys stored in the directory for potential compromise
• Review LDAP access logs for evidence of exploitation attempts
• Consider rotating BitLocker recovery keys for critical systems if compromise is suspected

Patch Information

The Samba project has released security updates addressing this vulnerability. Organizations should upgrade to versions 4.16.10, 4.17.7, 4.18.1 or later. Detailed patch information and security advisory are available from the Samba Security Advisory. Additional advisories have been published by Gentoo, Fedora, and NetApp.

Workarounds

• If immediate patching is not possible, consider restricting LDAP access to only essential administrative users
• Implement network segmentation to limit which systems can directly query the Samba AD DC
• Temporarily relocate BitLocker recovery keys to a separate secure storage system
• Enable enhanced LDAP audit logging to detect and respond to exploitation attempts

# Check current Samba version
samba --version

# Verify patched version after upgrade
# Expected: Version 4.16.10, 4.17.7, 4.18.1 or later
smbd --version

# Enable enhanced LDAP logging for monitoring
# Add to smb.conf under [global] section
# log level = 3 auth:5 ldap:5