CVE-2026-27738
📋 TL;DR
An open redirect vulnerability in Angular SSR allows attackers to manipulate URLs when applications are deployed behind proxies that pass unsanitized X-Forwarded-Prefix headers. This enables phishing and SEO hijacking attacks by redirecting users to malicious sites. Only Angular SSR applications with specific configurations are affected.
💻 Affected Systems
- Angular SSR (Server-Side Rendering)
⚠️ Manual Verification Required
This CVE does not have specific version information in our database, so automatic vulnerability detection cannot determine if your system is affected.
Why? The CVE database entry doesn't specify which versions are vulnerable (no version ranges provided by the vendor/NVD).
🔒 Custom verification scripts are available for registered users. Sign up free to download automated test scripts.
- Review the CVE details at NVD
- Check vendor security advisories for your specific version
- Test if the vulnerability is exploitable in your environment
- Consider updating to the latest version as a precaution
⚠️ Risk & Real-World Impact
Worst Case
Large-scale phishing campaigns redirecting legitimate users to malicious sites, credential theft, SEO hijacking affecting search rankings.
Likely Case
Targeted phishing attacks against application users, SEO manipulation for competitive advantage.
If Mitigated
No impact if proper header sanitization or patched versions are deployed.
🎯 Exploit Status
Exploitation requires specific infrastructure configuration but is straightforward once conditions are met.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 21.2.0-rc.1, 21.1.5, 20.3.17, 19.2.21
Vendor Advisory: https://github.com/angular/angular-cli/security/advisories/GHSA-xh43-g2fq-wjrj
Restart Required: Yes
Instructions:
1. Update Angular CLI to patched version. 2. Update Angular packages. 3. Rebuild and redeploy application. 4. Restart SSR server.
🔧 Temporary Workarounds
Sanitize X-Forwarded-Prefix Header
allAdd middleware to sanitize X-Forwarded-Prefix header before Angular SSR processes request
// In server.ts, add header sanitization before Angular engine processes request
// Remove or sanitize X-Forwarded-Prefix header values starting with ///
🧯 If You Can't Patch
- Implement reverse proxy/CDN configuration to strip or sanitize X-Forwarded-Prefix headers
- Disable internal redirect routes or implement additional validation for redirect URLs
🔍 How to Verify
Check if Vulnerable:
Check Angular CLI version and verify if application uses SSR with X-Forwarded-Prefix header passing through proxyCheck Version:
ng versionVerify Fix Applied:
Verify Angular CLI version is patched and test with malicious X-Forwarded-Prefix header values📡 Detection & Monitoring
Log Indicators:
- Unusual X-Forwarded-Prefix header values starting with ///
- Unexpected redirect patterns in application logs
Network Indicators:
- HTTP requests with X-Forwarded-Prefix: /// in headers
- Redirects to external domains from internal routes
SIEM Query:
http.headers:X-Forwarded-Prefix="///*" OR http.status_code=302 AND NOT url.domain:internal-domain.com🔗 References
- https://github.com/angular/angular-cli/commit/877f017ace4b83277d773aa37f5813e5e9faec7e
- https://github.com/angular/angular-cli/issues/32501
- https://github.com/angular/angular-cli/pull/32521
- https://github.com/angular/angular-cli/security/advisories/GHSA-xh43-g2fq-wjrj
- https://github.com/angular/angular-cli/issues/32501
