HTTP Header Injection / XSS in Apache ActiveMQ MessageServlet
CVE-2026-42253 is an input neutralization flaw in Apache ActiveMQ and Apache ActiveMQ Web affecting the web console API MessageServlet. The servlet copies JMS message properties directly into HTTP response headers without validation or sanitization. Because attacker-controlled JMS message properties can be reflected into response headers, an attacker can overwrite or inject security-relevant headers in responses generated by the servlet. The issue is described as a cross-site scripting vulnerability and affects Apache ActiveMQ and Apache ActiveMQ Web before 5.19.7, and versions 6.0.0 through 6.2.5.
Are you exposed to this one?
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Impact, mitigation & remediation
What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.
Impact
What an attacker gets, and what they’ve been doing with it.
Mitigation
If you can’t patch tonight, do this now.
Remediation
Patch, then assume compromise.
Exploits
No public exploits tracked yet. Mallory keeps watching.
No public exploit code observed for this vulnerability.
Affected products & vendors
Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.
Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.
Recent activity
8 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
An HTTP response header injection vulnerability in Apache ActiveMQ and Apache ActiveMQ Web caused by improper handling of JMS message properties in MessageServlet, potentially enabling XSS, response manipulation, session hijacking, and clickjacking.
An Apache ActiveMQ input validation flaw in MessageServlet that allows header injection and can enable cross-site scripting by copying unsanitized message attributes into HTTP response headers.
The version that knows your environment.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.