The vulnerability in n8n involves the expression compiler sanitizer that resolves through a dynamically scoped this and does not reject reserved class member names. Specifically, a class field named __sanitize can rebind the sanitizer and access the Function constructor, allowing an attacker to execute arbitrary code on the backend and within the editor preview. The affected code is in the PrototypeSanitizer AST hook located in packages/workflow/src/expression-sandboxing.ts. The issue is addressed in versions 1.123.76, 2.37.7, and 2.38.2.

Successful exploitation allows an attacker with limited privileges to execute arbitrary backend code and JavaScript in the editor preview, potentially leading to full compromise of the affected system. The CVSS 4.0 score of 8.7 reflects high impact with network attack vector, low attack complexity, and partial privileges required.

This vulnerability is fixed in n8n versions 1.123.76, 2.37.7, and 2.38.2. Users should upgrade to these or later versions to remediate the issue. No vendor advisory is provided to indicate alternative mitigations or temporary fixes. Patch status is not explicitly confirmed beyond the fixed versions; users should verify with official n8n release notes.