External risk intelligence

Apache Artemis Session Hijacking Vulnerability.

CVE advisorySeverity: CRITICAL (CVSS 9.8)

CVE-2026-57967

Apache ActiveMQ Artemis is a message broker. While these are often deployed in internal network segments for application-to-application communication, they are occasionally exposed to the internet or wide-area networks to facilitate distributed messaging, making internet reachability possible depending on the specific architectural deployment.

Missing Authentication

Halo Surface Signal: 3 out of 5 — possibly public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

A security vulnerability has been identified in Apache Artemis and Apache ActiveMQ Artemis message brokers that allows an unauthenticated attacker to take over existing sessions. This could potentially lead to unauthorized access and control over ongoing operations.

Session hijacking allows unauthorized control.
Critical infrastructure may use this technology.
Assess exposure and relevant systems.

Attack Path

How an attacker could exploit the issue

An unauthenticated attacker can craft a specific network packet to hijack an existing session in Apache Artemis or ActiveMQ Artemis. This allows the attacker to take over the ongoing execution of a previously authenticated session without needing any credentials.

Network access required.
Crafted CORE protocol packet triggers vulnerability.
Hijack existing sessions, assume execution.

Live Threat

Current exploitation, exposure, and threat context

An unauthenticated attacker could steal an existing session by crafting a specific network packet to an Apache Artemis or Apache ActiveMQ Artemis message broker. This could allow the attacker to assume the identity and ongoing execution of a previously authenticated session, potentially impacting the integrity and availability of services reliant on the broker.

Asset at risk: Message broker sessions.
How exposure could happen: Crafting a malicious packet.
Realistic consequence: Session hijacking and unauthorized access.

Operational Fix

Recommended remediation, mitigation, and detection steps

This vulnerability in Apache Artemis allows unauthenticated remote attackers to hijack existing sessions by crafting a specific packet. In a typical deployment, platform or infrastructure teams responsible for the message broker would likely manage the affected technology. The first practical step is to identify all instances of the broker, determine their reachability and criticality, and then locate the accountable owner to plan remediation based on risk.

Platform/Infrastructure teams own the issue.
Verify affected broker reachability and criticality.
Plan upgrades during the next maintenance window.

Supplementary metadata

CVSS vector

Validate whether this threat affects your internet-facing exposure.

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Frequently asked questions

What is Apache Artemis?

Apache Artemis and ActiveMQ Artemis are message brokers used to facilitate communication between different software applications. They act as a central hub for exchanging messages, often serving as the backbone for distributed systems, microservices, and asynchronous task processing. Organizations rely on them to ensure reliable data transit across complex, modern application environments.

How does CVE-2026-57967 allow session hijacking?

This vulnerability is classified as CWE-306, which relates to a missing authentication for a critical function. Because the broker fails to verify the requester's identity for the SESSION_REATTACH operation, an attacker can use a specially crafted network packet to impersonate an existing, authorized user. Once the attacker successfully hijacks the session, they can perform actions as if they were the legitimate, already-authenticated client.

Does any specific action trigger this vulnerability?

The flaw is triggered by an attacker sending a malformed CORE protocol SESSION_REATTACH packet directly to the message broker. This does not require the attacker to have valid login credentials or prior access to the system. Conversely, simply connecting to the broker or sending standard, non-malicious traffic will not trigger this specific hijacking behavior.

Is my instance at risk according to Halo Surface Signal?

Halo Surface Signal notes that while these brokers are often kept within internal network segments for private application-to-application traffic, they are sometimes configured with internet or wide-area network accessibility. If your broker is reachable from outside your trusted network, the risk of an unauthenticated remote attacker attempting to hijack a session is significantly increased.

Do I need to update my message broker?

Yes. The recommended path is to upgrade to version 2.57.0, which addresses this security flaw. Before applying the update, identify all instances of Apache Artemis or ActiveMQ Artemis within your infrastructure, assess their network reachability, and coordinate with the teams responsible for these systems to schedule the upgrade during your next maintenance window.

References

Written by Nicholas Merritt

Nicholas Merritt is VP of Security Solutions at Halo Security. With more than 25 years across application security, vulnerability prioritization, and offensive security, he helps teams translate threat data into practical exposure validation and remediation focus. He authors Halo Threat Intelligence CVE advisories using Halo Surface Signal and H/A/L/O context to prioritize internet-facing risk.