CVE-2025-62595
📋 TL;DR
This CVE describes a URL redirect bypass vulnerability in Koa.js middleware for Node.js. Attackers can manipulate the Referer header to force user browsers to navigate to malicious external websites, enabling phishing and social engineering attacks. Applications using Koa.js versions 2.16.2 to before 2.16.3 or 3.0.1 to before 3.0.3 are affected.
💻 Affected Systems
- Koa.js
📦 What is this software?
Koa by Koajs
Koa by Koajs
⚠️ Risk & Real-World Impact
Worst Case
Users are redirected to sophisticated phishing sites that steal credentials, session tokens, or install malware, leading to account compromise and data breaches.
Likely Case
Users are redirected to phishing pages attempting to harvest login credentials or personal information through social engineering.
If Mitigated
With proper input validation and security headers, the impact is limited to failed redirect attempts or blocked navigation.
🎯 Exploit Status
Exploitation requires manipulating HTTP Referer headers and depends on application using vulnerable redirect functionality.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 2.16.3 or 3.0.3
Vendor Advisory: https://github.com/koajs/koa/security/advisories/GHSA-g8mr-fgfg-5qpc
Restart Required: Yes
Instructions:
1. Update Koa.js dependency in package.json to ^2.16.3 or ^3.0.3. 2. Run 'npm update koa' or 'yarn upgrade koa'. 3. Restart your Node.js application.
🔧 Temporary Workarounds
Implement custom redirect validation
allAdd middleware to validate and sanitize redirect URLs before processing Referer headers.
// Example middleware to validate redirects
app.use(async (ctx, next) => {
const referer = ctx.get('Referer');
if (referer && !isSafeUrl(referer)) {
ctx.throw(400, 'Invalid redirect URL');
}
await next();
});
🧯 If You Can't Patch
- Implement Content Security Policy (CSP) with strict directives to restrict navigation
- Deploy WAF rules to block malicious Referer headers containing external URLs
🔍 How to Verify
Check if Vulnerable:
Check package.json or run 'npm list koa' to see if version is between 2.16.2-2.16.2 or 3.0.1-3.0.2.Check Version:
npm list koa | grep koaVerify Fix Applied:
Confirm Koa version is 2.16.3 or higher for v2, or 3.0.3 or higher for v3 using 'npm list koa'.📡 Detection & Monitoring
Log Indicators:
- Unusual Referer headers containing external domains
- Multiple 302/303 redirect responses to external URLs
Network Indicators:
- HTTP requests with manipulated Referer headers pointing to unexpected domains
SIEM Query:
http.referer CONTAINS "http://" OR "https://" AND NOT CONTAINS "yourdomain.com"