CVE-2026-67312

axios versions from 0.28.0 before 0.33.0 and from 1.0.0 before 1.18.0 contain uncontrolled recursion in formDataToJSON (exposed as axios.formToJSON() and used internally when serializing FormData with Content-Type: application/json). When an application passes attacker-controlled FormData field names, a field name with thousands of nested bracket-delimited segments causes unbounded recursion in buildPath(), exhausting the JavaScript call stack (RangeError: Maximum call stack size exceeded) and causing denial of service for that request, or process termination in applications without appropriate error handling.

axios versions from 0.28.0 before 0.33.0 and from 1.0.0 before 1.18.0 contain uncontrolled recursion in formDataToJSON (exposed as axios.formToJSON() and used internally when serializing FormData with Content-Type: application/json). When an application passes attacker-controlled FormData field names, a field name with thousands of nested bracket-delimited segments causes unbounded recursion in buildPath(), exhausting the JavaScript call stack (RangeError: Maximum call stack size exceeded) and causing denial of service for that request, or process termination in applications without appropriate error handling.

Duplicate Advisory

This advisory has been withdrawn because it is a duplicate of GHSA-pmv8-rq9r-6j72. This link is maintained to preserve external references.

Original Description

axios versions from 0.28.0 before 0.33.0 and from 1.0.0 before 1.18.0 contain uncontrolled recursion in formDataToJSON (exposed as axios.formToJSON() and used internally when serializing FormData with Content-Type: application/json). When an application passes attacker-controlled FormData field names, a field name with thousands of nested bracket-delimited segments causes unbounded recursion in buildPath(), exhausting the JavaScript call stack (RangeError: Maximum call stack size exceeded) and causing denial of service for that request, or process termination in applications without appropriate error handling.

Summary

Axios versions starting with 0.28.0 contain uncontrolled recursion in formDataToJSON, which is exposed as axios.formToJSON() and used internally when axios serialises FormData with Content-Type: application/json.

If an application passes attacker-controlled FormData field names to this functionality, a field name with thousands of nested bracket segments can exhaust the JavaScript call stack and cause denial of service for that request or, in applications without appropriate error handling, process termination.

Impact

Applications are affected only when untrusted users can control FormData key names that are converted through axios.

Affected paths include direct use of axios.formToJSON() on untrusted FormData and axios requests in which attacker-controlled FormData is sent with Content-Type: application/json.

The observed failure is RangeError: Maximum call stack size exceeded. In local testing, this error is catchable, so process-wide crash depends on the consuming application's error handling and runtime behaviour.

Affected Functionality

Affected functionality:

• axios.formToJSON(formData)
• Named ESM export formToJSON
• Default transformRequest behaviour for FormData when Content-Type contains application/json

Unaffected functionality:

• Normal multipart FormData submission without JSON serialisation
• toFormData, which already enforces a maxDepth guard
• Axios versions <=0.27.2, where formDataToJSON was not present

Technical Details

The vulnerable code is in lib/helpers/formDataToJSON.js.

parsePropPath() splits a field name such as a[x][x][x] into path segments. buildPath() then recursively processes one segment per call without enforcing a maximum depth:

const result = buildPath(path, value, target[name], index);

A key with thousands of bracket-delimited segments causes thousands of recursive calls and can exceed the JavaScript engine's call stack limit.

Relevant source locations:

• lib/helpers/formDataToJSON.js contains the unbounded recursive buildPath().
• lib/axios.js exposes the helper as axios.formToJSON.
• index.js exposes formToJSON as a named export.
• index.d.ts and index.d.cts declare the public API.
• lib/defaults/index.js calls formDataToJSON(data) when JSON-serializing FormData.

The inverse helper, toFormData, already enforces maxDepth and throws AxiosError with ERR_FORM_DATA_DEPTH_EXCEEDED, but formDataToJSON does not have an equivalent guard.

Proof of Concept of Attack

import axios from 'axios';

const fd = new FormData();
fd.append('a' + '[x]'.repeat(15000), 'value');

try {
  axios.formToJSON(fd);
  console.log('not vulnerable');
} catch (e) {
  console.log(`${e.constructor.name}: ${e.message}`);
}

Expected result on affected versions:

RangeError: Maximum call stack size exceeded

The same condition can be reached via an axios request transformation when attacker-controlled FormData is sent with Content-Type: application/json.

Workarounds

Applications can reject or normalise untrusted form field names before calling axios.formToJSON().

Applications can avoid sending untrusted FormData through axios as JSON unless JSON conversion is required.

Applications should catch errors around formToJSON() or axios requests that transform untrusted FormData.

<details> <summary>Original Source</summary>

Summary

An uncontrolled recursion vulnerability in formDataToJSON allows any user who controls FormData input to crash a Node.js process with a single request. The function recurses once per bracket-delimited segment in a FormData key name with no depth limit, so a key like a[x][x][x]... with 15,000+ segments exhausts the call stack. This is a denial-of-service that kills the process via an unrecoverable RangeError. The inverse function toFormData already enforces a maxDepth limit (default 100) for exactly this reason — formDataToJSON…

axios versions from 0.28.0 before 0.33.0 and from 1.0.0 before 1.18.0 contain uncontrolled recursion in formDataToJSON (exposed as axios.formToJSON() and used internally when serializing FormData with Content-Type: application/json). When an application passes attacker-controlled FormData field names, a field name with thousands of nested bracket-delimited segments causes unbounded recursion in buildPath(), exhausting the JavaScript call stack (RangeError: Maximum call stack size exceeded) and causing denial of service for that request, or process termination in applications without appropriate error handling.

axios versions from 0.28.0 before 0.33.0 and from 1.0.0 before 1.18.0 contain uncontrolled recursion in formDataToJSON (exposed as axios.formToJSON() and used internally when serializing FormData with Content-Type: application/json). When an application passes attacker-controlled FormData field names, a field name with thousands of nested bracket-delimited segments causes unbounded recursion in buildPath(), exhausting the JavaScript call stack (RangeError: Maximum call stack size exceeded) and causing denial of service for that request, or process termination in applications without appropriate error handling.