Leading control characters in a URL are not stripped when passed into url-parse. This can cause input URLs to be mistakenly be interpreted as a relative URL without a hostname and protocol, while the WHATWG URL parser will trim control characters and treat it as an absolute URL.
If url-parse is used in security decisions involving the hostname / protocol, and the input URL is used in a client which uses the WHATWG URL parser, the decision may be incorrect.
This can also lead to a cross-site scripting (XSS) vulnerability if url-parse is used to check for the javascript: protocol in URLs. See following example:
const parse = require('url-parse')
const express = require('express')
const app = express()
const port = 3000
url = parse(\"\\bjavascript:alert(1)\")
console.log(url)
app.get('/', (req, res) => {
if (url.protocol !== \"javascript:\") {res.send(\"<a href=\\'\" + url.href + \"\\'>CLICK ME!</a>\")}
})
app.listen(port, () => {
console.log(`Example app listening on port ${port}`)
})
References
Leading control characters in a URL are not stripped when passed into url-parse. This can cause input URLs to be mistakenly be interpreted as a relative URL without a hostname and protocol, while the WHATWG URL parser will trim control characters and treat it as an absolute URL.
If url-parse is used in security decisions involving the hostname / protocol, and the input URL is used in a client which uses the WHATWG URL parser, the decision may be incorrect.
This can also lead to a cross-site scripting (XSS) vulnerability if url-parse is used to check for the javascript: protocol in URLs. See following example:
References