CVE-2026-39842: OpenRemote is an open-source IoT platform. Versions 1.21.0 and below contain two interrelated expression injection vulnerabilities in the rules engine...

Description

OpenRemote is an open-source IoT platform. Versions 1.21.0 and below contain two interrelated expression injection vulnerabilities in the rules engine that allow arbitrary code execution on the server. The JavaScript rules engine executes user-supplied scripts via Nashorn's ScriptEngine.eval() without sandboxing, class filtering, or access restrictions, and the authorization check in RulesResourceImpl only restricts Groovy rules to superusers while leaving JavaScript rules unrestricted for any user with the write:rules role. Additionally, the Groovy rules engine has a GroovyDenyAllFilter security filter that is defined but never registered, as the registration code is commented out, rendering the SandboxTransformer ineffective for superuser-created Groovy rules. A non-superuser attacker with the write:rules role can create JavaScript rulesets that execute with full JVM access, enabling remote code execution as root, arbitrary file read, environment variable theft including database credentials, and complete multi-tenant isolation bypass to access data across all realms. This issue has been fixed in version 1.22.0.

Metrics

CVSS 3.1

9.9/10

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

EPSS Probability

0.92%

55.9th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Openremote	Openremote	< 1.22.0

References

https://github.com/openremote/openremote/releases/tag/1.22.0Product, Release Notes
https://github.com/openremote/openremote/security/advisories/GHSA-7mqr-33rv-p3mpExploit, Vendor Advisory

Timeline

Published: Apr 15, 2026
Last Modified: Jun 17, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2026-39842?

OpenRemote is an open-source IoT platform. Versions 1.21.0 and below contain two interrelated expression injection vulnerabilities in the rules engine that allow arbitrary code execution on the server. The JavaScript rules engine executes user-supplied scripts via Nashorn's ScriptEngine.eval() without sandboxing, class filtering, or access restrictions, and the authorization check in RulesResourceImpl only restricts Groovy rules to superusers while leaving JavaScript rules unrestricted for any user with the write:rules role. Additionally, the Groovy rules engine has a GroovyDenyAllFilter security filter that is defined but never registered, as the registration code is commented out, rendering the SandboxTransformer ineffective for superuser-created Groovy rules. A non-superuser attacker with the write:rules role can create JavaScript rulesets that execute with full JVM access, enabling remote code execution as root, arbitrary file read, environment variable theft including database credentials, and complete multi-tenant isolation bypass to access data across all realms. This issue has been fixed in version 1.22.0.

How severe is CVE-2026-39842?

CVE-2026-39842 has a CVSS score of 9.9/10 (CRITICAL severity). The EPSS model estimates a 0.92% probability of exploitation in the next 30 days.

How do I fix CVE-2026-39842?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.