CVE-2026-49434: Apache ActiveMQ LDAP Input Validation – HIGH Severity Patch Alert

Technical summary

CVE-2026-49434 is an improper input validation vulnerability (CWE-20) affecting Apache ActiveMQ's LDAP-based configuration mechanism. When a broker is configured to use LDAP for authentication or transport discovery, an attacker with write privileges to LDAP entries within the configured searchBase and searchFilter scope can craft malicious entries that bypass transport restrictions. The broker fails to properly validate these entries before instantiating the specified transport and retrieving configuration from attacker-controlled sources. This results in arbitrary BrokerService instantiation within the broker JVM, potentially allowing further lateral movement or data exfiltration.

Business impact

A successful attack enables an attacker to create a rogue message broker inside your production broker JVM. This can be leveraged to intercept, modify, or redirect messaging traffic, compromise message confidentiality and integrity, and establish a foothold for further attacks on dependent applications. Organizations relying on ActiveMQ for critical messaging workflows face disruption and potential data breach if an attacker gains LDAP write access.

Affected systems

Apache ActiveMQ versions before 5.19.8 and versions 6.0.0 through 6.2.6 are vulnerable. The vulnerability applies across all three affected product lines: Apache ActiveMQ Broker, Apache ActiveMQ, and Apache ActiveMQ All. Any deployment using LDAP-based transport or authentication configuration is at risk if LDAP write access is available to hostile actors.

Exploitability

Exploitation requires prior LDAP write access to entries matching the broker's configured searchBase and searchFilter. This is a reasonable prerequisite in compromised or insider-threat scenarios, but not trivial in well-segmented networks. Once LDAP write access is obtained, exploitation is straightforward and requires no special broker privileges or user interaction. The attack surface is limited to organizations using LDAP integration with ActiveMQ.

Remediation

Upgrade Apache ActiveMQ to version 5.19.8 or 6.2.7 immediately. These versions include input validation fixes that prevent malicious LDAP entries from instantiating unauthorized transports. Organizations unable to upgrade immediately should restrict LDAP write access to trusted administrators only, disable LDAP-based transport configuration if not required, and monitor LDAP modifications for suspicious activity.

Patch guidance

Apply security updates as follows: for ActiveMQ 5.x deployments, upgrade to 5.19.8 or later; for 6.x deployments, upgrade to 6.2.7 or later. Verify against the official Apache ActiveMQ security advisory for complete patch details and any version-specific deployment notes. Test patches in a non-production environment before rolling out to production brokers. Ensure all broker instances in a cluster are updated to prevent mixed-version vulnerabilities.

Detection guidance

Monitor LDAP logs for unexpected modifications to entries within your configured searchBase that correspond to transport or broker configuration. Watch broker logs for unauthorized BrokerService instantiation attempts or unexpected transport binding events. Implement LDAP access controls to alert on write operations from non-administrative accounts. Network monitoring can detect unusual outbound connections initiated by the broker to fetch remote configurations.

Why prioritize this

This vulnerability scores HIGH (7.5 CVSS) and warrants prioritization because it enables integrity compromise of the messaging infrastructure with minimal prerequisites once LDAP write access is obtained. While not currently listed in the KEV catalog, the attack surface in organizations using LDAP with ActiveMQ is significant. Patching is straightforward and low-risk, making this a high-return remediation effort.

Risk score, explained

The CVSS 3.1 score of 7.5 reflects a network-accessible vulnerability with no authentication required from the ActiveMQ side (though LDAP write access is a prerequisite). The vector AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N indicates that integrity is severely impacted (ability to inject a rogue broker) while confidentiality and availability are not directly affected by this mechanism alone. The score is elevated by the high impact of successful exploitation despite the LDAP write access requirement.

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