Executive brief
n8n is a workflow automation platform that allows users to create and execute complex data processing pipelines. The legacy expression engine in n8n contains a vulnerability where malicious expressions can tamper with the global JSON.stringify function during code generation, allowing attackers to inject arbitrary executable code. An authenticated user with access to the platform can exploit this to achieve remote code execution on the n8n server.
Technical details
The vulnerability is a code injection flaw (CWE-94) affecting n8n's legacy expression engine. During expression code generation, two stages call the global JSON.stringify function: the compiler when printing synthetic string literals, and the isolate bridge when interpolating timezone values into per-evaluation wrappers. An attacker can craft an expression that replaces the global JSON.stringify, causing the code-generation stages to produce malicious executable source code instead of literal data. The attack requires low privileges (authenticated user) and network access to the n8n instance. The vm expression engine (default in patched versions) is not affected. The fix captures a reference to JSON.stringify at module load time, preventing later global state modifications from altering generated code.
Affected products
- n8n n8n < 1.123.76, >= 2.0.0 < 2.37.7, >= 2.38.0 < 2.38.2
Timeline
- 2026-09-10: disclosed: Vulnerability published on GitHub Advisory Database
- 2026-09-10: patched: Patches released: n8n 1.123.76, 2.37.7, and 2.38.2
References
- https://api.github.com/users/hiddingtrojans
- https://github.com/hiddingtrojans
- https://api.github.com/users/hiddingtrojans/gists%7B/gist_id%7D
- https://api.github.com/users/hiddingtrojans/repos
- https://avatars.githubusercontent.com/u/107155157?v=4
- https://api.github.com/users/hiddingtrojans/events%7B/privacy%7D