multipart/form-data Unable to calculate form data length

[PhilippGoetje]

Bug Description

Hey,

in the last 2-3 updates, the http multipart/form-data with n8n binary data broke.
When I copy the same workflow with the same data to an older version, it works. Till a few days ago, I had no issues. Now I get the following message in the logs:
Mar 05 12:43:49 Unable to calculate form data length
Mar 05 12:43:49 data should be a string, Buffer or Uint8Array
Mar 05 12:44:52 Unable to calculate form data length
Mar 05 12:44:52 data should be a string, Buffer or Uint8Array

Version 2.10.3 self hosted via claudron.

To Reproduce

1. set up a flow to get a binary file and merge via merge node with other data.
2. Send binary file as multipart/form-data with two properties. "name" as string and "value" as data (binary)
3. Node never finishes, does not throw an error and eventually runs into timeout.

Expected behavior

Working as before, where no issue was present

Debug Info

Mar 05 12:18:19 Version: 2.10.3
Mar 05 12:43:49 Unable to calculate form data length
Mar 05 12:43:49 data should be a string, Buffer or Uint8Array
Mar 05 12:44:52 Unable to calculate form data length
Mar 05 12:44:52 data should be a string, Buffer or Uint8Array

Operating System

Claudron

n8n Version

2.10.3

Node.js Version

Package version 4.9.1 on claudron, dont know the node.js version

Database

PostgreSQL

Execution mode

main (default)

Hosting

self hosted

[n8n-assistant]

Hey @PhilippGoetje,

Thank you for reaching out! We’ve received your issue and are looking into it. To help us track this internally, we’ve created a Linear ticket with the reference: "GHC-7122".

We’ll keep you updated as we make progress, but if you have any additional details or context to share, feel free to add them here - it’s always helpful!

Thanks for your patience and for bringing this to our attention.

---

For INTERNAL use only: GHC-7122

[PhilippGoetje]

The oder version that still works is 2.9.2. I do not have access/time to test others.

[PhilippGoetje]

Maybe this error message helps, this is the trace that I get on error email handling.

{"context":{},"item":{"json":{"filename":"Foto 2025-12-04 14-35-05.jpg","error":{"message":"timeout of 60000ms exceeded","name":"AxiosError","stack":"AxiosError: timeout of 60000ms exceeded\n at RedirectableRequest.handleRequestTimeout (/app/code/node_modules/axios/lib/adapters/http.js:857:15)\n at RedirectableRequest.emit (node:events:518:28)\n at Timeout._onTimeout (/app/code/node_modules/follow-redirects/index.js:221:12)\n at listOnTimeout (node:internal/timers:588:17)\n at processTimers (node:internal/timers:523:7)\n at Axios.request (/app/code/node_modules/axios/lib/core/Axios.js:46:41)\n at processTicksAndRejections (node:internal/process/task_queues:105:5)\n at invokeAxios (/app/code/node_modules/n8n-core/src/execution-engine/node-execution-context/utils/request-helper-functions.ts:303:10)\n at proxyRequestToAxios (/app/code/node_modules/n8n-core/src/execution-engine/node-execution-context/utils/request-helper-functions.ts:684:20)\n at Object.request (/app/code/node_modules/n8n-core/src/execution-engine/node-execution-context/utils/request-helper-functions.ts:1841:4)","code":"ECONNABORTED"}},"pairedItem":{"item":0}},"params":{"curlImport":"","method":"POST","url":"={{ $('Execute Workflow Trigger').first().json.url + $('Execute Workflow Trigger').first().json.recordId+ '/files'}}","authentication":"none","provideSslCertificates":false,"sendQuery":false,"sendHeaders":true,"specifyHeaders":"keypair","headerParameters":{"parameters":[{"name":"Authorization","value":"={{ $('Execute Workflow Trigger').item.json.secret }}"},{"name":"Content-Type","value":"multipart/form-data"}]},"sendBody":true,"contentType":"multipart-form-data","bodyParameters":{"parameters":[{"parameterType":"formBinaryData","name":"file","inputDataFieldName":"data"},{"parameterType":"formData","name":"fieldId","value":"={{ $('Execute Workflow Trigger').first().json.targetFieldId }}"}]},"options":{"timeout":60000},"infoMessage":""}}

[disassembledd]

@PhilippGoetje, do you happen to be running in queue mode? Could you attempt setting the body type to Binary instead of Form-Data as mentioned in #25567 to see if that resolves? I'm looking to see if these are related issues.

#triage:in-progress