CVE-2019-5648

Executive Summary

CVE-2019-5648 is a credential exposure vulnerability in Barracuda Load Balancer ADC devices running unpatched firmware versions up to and including v6.4. An authenticated administrative user can modify the LDAP service configuration to redirect the connector to an attacker-controlled LDAP server without being required to re-enter LDAP credentials, thereby exposing the stored credentials over the network. This vulnerability carries a CVSS score of 8.7 and affects all Barracuda Load Balancer ADC deployments relying on LDAP authentication that have not applied available firmware patches.

Technical Analysis

Barracuda Load Balancer ADC is an application delivery controller that includes LDAP integration for authentication and user management. The vulnerability resides in the LDAP connector configuration module, where administrative users have the ability to edit LDAP service settings.

The core flaw is that when an authenticated administrator changes the LDAP server target, the device does not prompt for re-authentication or re-entry of the LDAP bind credentials. The credentials remain associated with the configuration and are transmitted to the newly specified LDAP server endpoint.

Vulnerability Class: This is a credential exposure issue falling under CWE-522 (Insufficiently Protected Credentials). The attack mechanism is as follows:

1. An attacker with administrative access to the device's management interface navigates to the LDAP configuration section.
2. The attacker modifies the LDAP server address to point to a system under their control.
3. Since the existing LDAP credentials are retained in the configuration without requiring re-entry, the device will transmit those credentials to the attacker-controlled LDAP server during the next LDAP binding attempt.

The NVD description specifically states the affected firmware is "unpatched firmware <= v6.4" and that the change can be performed "without having to re-enter LDAP credentials," confirming that the credentials persist in the configuration and are exposed to the new endpoint.

Attack Surface: The vulnerability is reachable through the administrative web interface of the Barracuda Load Balancer ADC. Authentication is required (CVSS Privileges Required: High), meaning the attacker needs valid administrative credentials for the device. This is a network-accessible attack vector (CVSS Attack Vector: Network).

Technical constraints from available data:

• The exact endpoint or function name for LDAP configuration is not disclosed in the NVD description.
• The protocol used for credential transmission (e.g., LDAP bind, LDAPS, or plaintext) is not specified.
• No code-level details, function names, or file paths are available for the LDAP configuration module.

The patch confidence is 2/4 (CLAIMED), meaning only the CNA has confirmed a fix exists; this has not been independently verified. Patch availability is through Barracuda's automated security patching system for firmware versions 6.3.x and 6.4.x, with version 6.5 shipping with the fix.

Exploitation Scenarios

No public PoC is available; the attack chain is inferred from the vulnerability class and NVD description.

Scenario 1: Credential Harvesting via Rogue LDAP Server

1. Reconnaissance/Target Identification: The attacker identifies Barracuda Load Balancer ADC devices by scanning for the management interface on port 443 or other administrative ports. The attacker also determines if the device has unpatched firmware (<= v6.4) by fingerprinting the login page or response headers.

2. Authentication: The attacker obtains valid administrative credentials through prior compromise, password reuse, social engineering, or insider access.

3. Triggering the Flaw: The attacker logs into the management interface and navigates to the LDAP connector configuration section. The attacker changes the LDAP server hostname/IP from the legitimate directory server (e.g., a domain controller) to an attacker-controlled IP address.

4. Payload/Execution: The attacker sets up a rogue LDAP server that accepts connections. When the Barracuda device attempts to bind to the LDAP server (either during a periodic test, upon configuration save, or during a subsequent authentication request), it sends the stored LDAP bind credentials (username/password) to the attacker's server.

5. Post-Exploitation Impact: The attacker captures the LDAP credentials from the LDAP bind request. These credentials are typically privileged directory service accounts with substantial access rights to the enterprise directory. The attacker can then use these credentials to access the entire Active Directory/LDAP environment, potentially escalating to full domain compromise.

Scenario 2: Internal Redirection for Credential Capture

1. The attacker, as an authenticated admin, changes the LDAP server to point to another internal system they already control or have compromised.
2. The credentials are transmitted during LDAP bind operations as legitimate authentication requests occur (e.g., when users log into applications behind the load balancer).
3. The attacker passively captures credentials from this internal vantage point.

Scenario 3: Persistence Through Configuration Validation

1. After changing the LDAP server, the attacker may trigger a "test connection" feature (if available in the UI) to force immediate LDAP bind attempts.
2. Multiple bind attempts may occur, capturing credentials repeatedly or in various forms (e.g., simple bind vs. SASL).

Key constraints from the NVD description:

• Only authenticated administrative users can exploit this.
• The attack requires network access to the management interface.
• The specific LDAP settings changed are "the LDAP server" and the credentials are exposed "over the network."

No known threat actors have been observed exploiting this vulnerability in the wild, and it is not listed on the CISA KEV catalog.

Impact Assessment

CVSS Score: 8.7 (High) — The high score is driven by:

• Confidentiality (High): Exposure of LDAP bind credentials, which typically represent a privileged service account in the enterprise directory (often with read/write access to directory objects).
• Integrity (High): The attacker can modify LDAP configuration, redirecting authentication traffic and potentially causing service disruption.
• Availability (Low): Changing the LDAP server to an invalid/attacker-controlled endpoint could disrupt all services relying on LDAP authentication for legitimate users.
• Attack Complexity (Low): No special conditions beyond administrative access are required.
• Privileges Required (High): Administrative access to the device is required.

Blast Radius:

• Direct impact: Compromise of LDAP credentials used by the load balancer for directory integration.
• Secondary impact: The compromised LDAP credentials can compromise the entire directory service environment. If the bound account has delegated administrative privileges (common for service accounts), an attacker gains control over user accounts, group memberships, and potentially domain-level administrative access.
• Supply chain impact: For MSPs or service providers using Barracuda Load Balancer ADC, a compromise could expose credentials for multiple downstream customer environments if separate LDAP connectors are used.

Affected Systems:

• Barracuda Load Balancer ADC devices running firmware v6.4 or earlier.
• Any organization using LDAP authentication through the load balancer.
• Cloud and on-premises deployments where the management interface is exposed to untrusted networks.

Business Impact:

• Credential exfiltration leading to unauthorized directory access.
• Potential domain/AD compromise.
• Service disruption from misconfigured LDAP endpoints.
• Regulatory compliance failures (GDPR, HIPAA, PCI-DSS) due to credential exposure.

Detection Guidance

Sigma Rule

title: Barracuda Load Balancer ADC LDAP Configuration Change
id: d1a0c67e-9b3f-4b2e-9f1a-2c8d3e4f5a6b
status: experimental
description: Detects LDAP server configuration changes on Barracuda Load Balancer ADC which may indicate CVE-2019-5648 exploitation
logsource:
    product: barracuda
    service: loadbalancer
detection:
    selection:
        event_type: CONFIGURATION_CHANGE
        component: LDAP
        action: UPDATE
        field_modified: ldap_server
    condition: selection
level: high
falsepositives:
    - Legitimate administrative changes to LDAP configuration
tags:
    - attack.t1552
    - cve.2019-5648

YARA Rule

rule barracuda_ldap_cred_exposure_cve_2019_5648
{
    meta:
        author = "Valters IT Security Threat Intel"
        description = "Detects patterns in Barracuda Load Balancer ADC configuration files indicating modified LDAP server settings"
        cve = "CVE-2019-5648"
        date = "2025-01-01"
    strings:
        $s1 = "ldap_server" ascii nocase
        $s2 = "ldap_connector" ascii nocase
        $s3 = "ldap_bind_credentials" ascii nocase
        $s4 = "ldap" ascii nocase
        $s5 = "192.168." ascii
        $s6 = "10.0." ascii
    condition:
        uint16(0) == 0x5B7B or uint32(0) == 0x5B7B0A or filesize < 5MB and
        2 of ($s1,$s2,$s3) and ($s4) and (any of ($s5,$s6))
}

Note: The YARA rule focuses on configuration backup files or exported configuration archives that may be intercepted during exfiltration.

Suricata IDS Rule

alert http any any -> any any (msg:"CVE-2019-5648 Barracuda Load Balancer ADC LDAP Config Modification Attempt"; flow:to_server,established; content:"POST"; http_method; content:"/"; http_uri; content:"ldap"; http_uri; nocase; content:"server"; http_uri; nocase; pcre:"/ldap.*server.*(set|update|change|edit)/i"; classtype:attempted-admin; sid:2029001; rev:1; metadata:created_at 2025_01_01, updated_at 2025_01_01, cve CVE-2019-5648;)

Elastic Detection

// Detect configuration changes on Barracuda Load Balancer devices
// targeting LDAP server settings
configuration where
  event.action == "change" and
  process.name : "barracuda*" and
  message : "*ldap*" and
  (message : "*server*" or message : "*host*" or message : "*endpoint*") and
  message : "*changed*" or message : "*updated*" or message : "*modified*"

Splunk SPL Query

index=barracuda sourcetype="barracuda:loadbalancer:audit"
| search "LDAP" AND ("configuration" OR "modified" OR "changed" OR "updated")
| search "*server*" OR "*endpoint*" OR "*host*"
| table _time, src_ip, user, action, config_name, old_value, new_value
| where action="modify" AND config_name="ldap_server"
| eval severity="high"
| eval cve="CVE-2019-5648"

Wazuh OSSEC Rule

<group name="barracuda,ldap,">
    <rule id="100501" level="12">
        <decoded_as>json</decoded_as>
        <field name="device">barracuda_loadbalancer</field>
        <field name="component">LDAP</field>
        <field name="action">modify</field>
        <field name="field">server</field>
        <description>SCA: LDAP server configuration modified on Barracuda Load Balancer - possible CVE-2019-5648 exploitation</description>
        <group>att.t1552,cve.2019-5648,</group>
        <mitre>
            <id>T1552</id>
        </mitre>
    </rule>
</group>

Mitigation & Patch Guidance

Patch Confidence: 2/4 — CLAIMED (single source claims patch; not independently confirmed)

Immediate Mitigations (before patching)

1. Restrict management interface access: Limit access to the Barracuda Load Balancer ADC management interface to trusted administrative networks only. Disable direct internet exposure of the management port.
2. Rotate LDAP credentials: If any indication of unauthorized administrative access exists, rotate the LDAP bind credentials immediately and monitor for anomalous directory activity.
3. Enable audit logging: Verify that audit logging is enabled on the Barracuda device and that logs are forwarded to a SIEM for monitoring of configuration changes.
4. Monitor LDAP bind activity: Watch for bind attempts to unexpected or unknown LDAP server IP addresses from the load balancer.
5. Implement Multi-Factor Authentication (MFA): If supported, enforce MFA for administrative access to the device to reduce the risk of credential theft.

Patch/Upgrade Steps

1. Verify current firmware version: Confirm whether the device is running firmware v6.4 or earlier.
2. Apply available patches: Ensure the device is on either a 6.3.x or 6.4.x version so the patch can be applied through Barracuda's automated security patching system.
3. Verify automated patching is enabled: Confirm that the security update system has NOT been intentionally disabled on the device.
4. Upgrade to v6.5 or later: Version 6.5 ships with the patch for CVE-2019-5648. Plan the upgrade during a maintenance window.
5. Post-patch validation: After patching, verify the LDAP configuration settings and test LDAP authentication to ensure normal operation.
6. Contact Barracuda support: Confirm patch availability with Barracuda TAC, as the patch has not been independently confirmed by third parties.

Long-Term Hardening

1. Network segmentation: Place load balancer management interfaces on isolated management VLANs with strict firewall rules.
2. Least privilege access: Restrict administrative privileges to only those personnel who require them. Use separate accounts for device administration.
3. Credential vaulting: STore LDAP bind credentials in a secure credential management solution rather than embedding in device configuration.
4. Regular firmware updates: Establish a cadence for firmware updates, prioritizing security patches.
5. Configuration auditing: Regularly review device configuration for unauthorized changes, especially LDAP settings.
6. Harden LDAP communication: Configure LDAPS (LDAP over TLS) to encrypt credential transmission between the load balancer and directory servers.
7. Monitor threat landscape: Track Barracuda security advisories and subscribe to CVE notifications for future vulnerabilities.

References

1. NVD Entry: https://nvd.nist.gov/vuln/detail/CVE-2019-5648
2. Barracuda Security Advisory (CNA): Barracuda Networks security advisory for CVE-2019-5648 (LDAP Credential Exposure in Barracuda Load Balancer ADC)
3. MITRE CVE Record: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2019-5648
4. FIRST EPSS: https://www.first.org/epss/api — EPSS score 0.01125 (63.2nd percentile of actively exploited vulnerabilities)
5. CISA KEV Catalog: https://www.cisa.gov/known-exploited-vulnerabilities-catalog — Not listed; no known exploitation in the wild.

Threat actor campaigns: No known threat actor campaigns have been identified targeting CVE-2019-5648. The vulnerability is not listed in the CISA KEV catalog. No exploit code or PoC has been publicly released, and no Nuclei templates are available.