Atomicorp WAF Research Note: CVE-2026-42253

Apache ActiveMQ, Apache ActiveMQ Web: HTTP Response Header Injection via JMS Message Properties

CVE Details

• Already protected by existing Atomicorp WAF rules
• Protection status: Understanding Atomicorp WAF Protection Status
• CVE: CVE-2026-42253
• Name: Apache ActiveMQ, Apache ActiveMQ Web: HTTP Response Header Injection via JMS Message Properties
• Severity: Medium
• CVSS: 6.1 (v3.1) (Medium)
• CVSS version: 3.1
• CVSS source: NVD
• CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
  • Attack vector: Network
  • Attack complexity: Low
  • Privileges required: None
  • User interaction: Required
  • Scope: Changed
  • Confidentiality impact: Low
  • Integrity impact: Low
  • Availability impact: None
• CWE: CWE-79 — Improper Neutralization of Input During Web Page Generation (‘Cross-site Scripting’)
• Related CAPEC attack patterns (via MITRE CWE relationships): CAPEC-209 (opens in a new tab) , CAPEC-588 (opens in a new tab) , CAPEC-591 (opens in a new tab) , CAPEC-592 (opens in a new tab) , CAPEC-63 (opens in a new tab) , CAPEC-85 (opens in a new tab)
• Vendor: apache
• Vulnerable products: activemq , activemq web
• CVE published: 2026-06-01
• CVE last modified: 2026-07-22
• Affected versions (NVD configurations):
  • activemq: < 5.19.7
  • activemq: >= 6.0.0, < 6.2.6
  • activemq web: < 5.19.7
  • activemq web: >= 6.0.0, < 6.2.6
• EPSS: 0.0111; 63.9th percentile (FIRST (opens in a new tab) )
• Latest Update: 2026-09-06
• Selected Rule IDs observed: 333140 , 333141 , 340087 , 340099 , 340147 , 341099 , 341266
• Matching rules: 7; rules with blocking actions: 7
• Would-block Rule IDs: 333140 , 333141 , 340087 , 340099 , 340147 , 341099 , 341266
• Request surfaces inspected: JSON request data, Request URI, Request argument names, Request arguments, Request cookies, Request headers, SOAP request data, XML request data

Vulnerability Description

Improper Neutralization of Input During Web Page Generation (‘Cross-site Scripting’) vulnerability in Apache ActiveMQ, Apache ActiveMQ Web.

The MessageServlet in the ActiveMQ web console API copies every JMS message property into an HTTP response header without any validation. This can allow overwriting and injecting security headers by setting them on JMS messages that are returned by the servlet.

This issue affects Apache ActiveMQ: before 5.19.7, from 6.0.0 before 6.2.6; Apache ActiveMQ Web: before 5.19.7, from 6.0.0 before 6.2.6.

Users are recommended to upgrade to version 5.19.7 or 6.2.6, which fixes the issue. The MessageServlet has now been deprecated and disabled by default.

Recommended Actions

1. Maintain the observed Atomicorp protections. Keep your Atomicorp commercial rules current and confirm that the selected observed rules (333140 , 333141 , 340087 , 340099 , 340147 , 341099 , 341266 ) have not been locally disabled. Atomicorp commercial rules are enabled by default. If you use Atomic WAF, review the applicable policy and rule settings.

2. Apply the vendor’s remediation. WAF protection is defense in depth and does not replace upgrading or following the affected vendor’s guidance.

   • Affected versions: Apache Software Foundation Apache ActiveMQ versions earlier than 5.19.7.
   • Affected versions: Apache Software Foundation Apache ActiveMQ versions earlier than 6.2.6.
   • Affected versions: Apache Software Foundation Apache ActiveMQ Web versions earlier than 5.19.7.
   • Affected versions: Apache Software Foundation Apache ActiveMQ Web versions earlier than 6.2.6.
   • Recommended upgrade: Upgrade Apache Software Foundation Apache ActiveMQ to 5.19.7 or later.
   • Recommended upgrade: Upgrade Apache Software Foundation Apache ActiveMQ to 6.2.6 or later.
   • Recommended upgrade: Upgrade Apache Software Foundation Apache ActiveMQ Web to 5.19.7 or later.
   • Recommended upgrade: Upgrade Apache Software Foundation Apache ActiveMQ Web to 6.2.6 or later.

3. Validate after changes. Confirm rule updates are current, review WAF events for the affected application, and test application behavior after vendor upgrades, mitigations, or local policy changes.

Research Notes

Atomicorp WAF protections are designed around attack techniques and exploit behaviors, allowing existing protections to apply across multiple vulnerabilities without requiring a unique rule for every CVE.

Public Vulnerability References

• NVD (opens in a new tab)
• CVE Record (opens in a new tab)
• Vendor advisory: https://lists.apache.org/thread/j9vmlc410ht5f28fc98gx75jcbq62j00 (opens in a new tab)
• Exploit or technical research: http://www.openwall.com/lists/oss-security/2026/05/31/17 (opens in a new tab)

Test or Research Source

• Source: Atomicorp AI Research Framework
• Tags: cve, derived, waf-probe, xss

Research Note Context

This research note documents exploit-technique analysis associated with this vulnerability and references Atomicorp WAF protections observed during engineering review, testing, or validation activities.

Atomicorp security controls are generally designed to identify and mitigate attack techniques and exploit behaviors rather than individual CVE identifiers. As a result, protections developed for one vulnerability may also apply to related attack variants and future vulnerabilities using similar techniques.

Learn More

Atomicorp develops commercially supported security technologies for web applications, servers, endpoints, workloads, and legacy enterprise platforms.

Organizations interested in protecting systems against exploit techniques associated with vulnerabilities such as this one can learn more about:

• Atomic ModSecurity Rules: commercially maintained WAF rules for ModSecurity deployments, including protections for web attacks, bots, scanners, malware, exploitation attempts, and emerging vulnerability classes.
• Atomic WAF: an enterprise web application firewall with Atomicorp rules, centralized management, reporting, authentication controls, and operational tooling.
• Atomic ModSecurity Integrator: a special licensing option for MSPs, MSSPs, OEMs, VARs, reverse proxy providers, and other integrators who want to incorporate Atomicorp ModSecurity rule technology into their own products or services.
• Atomic OSSEC: an enterprise OSSEC-based intrusion detection, compliance, and security monitoring platform.
• Atomic Protector: workload protection for Linux, web, cloud, data center, and hybrid environments.

For additional information, product evaluations, or technical discussions, visit https://www.atomicorp.com/ or https://modsecurity.io/ (opens in a new tab) .