Affected: npm: axios

### Summary The `FormDataPart` constructor in `lib/helpers/formDataToStream.js` interpolates `value.type` directly into the `Content-Type` header of each multipart part without sanitizing CRLF (`\r\n`) sequences. An attacker who controls the `.type` property of a Blob/File-like object (e.g., via a user-uploaded file in a Node.js proxy service) can inject arbitrary MIME part headers into the multipart form-data body. This bypasses Node.js v18+ built-in header protections because the injection targets the multipart body structure, not HTTP request headers.

### Details In `lib/helpers/formDataToStream.js` at line 27, when processing a Blob/File-like value, the code builds per-part headers by directly embedding value.type: ``` if (isStringValue) { value = textEncoder.encode(String(value).replace(/\r?\n|\r\n?/g, CRLF)); } else { // value.type is NOT sanitized for CRLF sequences headers += `Content-Type: ${value.type || 'application/octet-stream'}${CRLF}`; } ``` Note that the string path (line above) explicitly sanitizes CRLF, but the binary/blob path does not. This inconsistency confirms the sanitization was intended but missed for `value.type`.

### Attack chain:

1. Attacker uploads a file to a Node.js proxy service, supplying a crafted MIME type containing `\r\n` sequences 2. The proxy appends the file to a FormData and posts it via `axios.post(url, formData)` 3. axios calls `formDataToStream()`, which passes `value.type` unsanitized into the multipart body 4. The down…