GHSA-m4w9-gch5-c2g4 is a medium-severity (CVSS 6.1) Open Redirect vulnerability in client-certificate-auth. A fix is available for client-certificate-auth — see the affected versions and patch details below.
client-certificate-auth Vulnerable to Open Redirect via Host Header Injection in HTTP-to-HTTPS redirect
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for GHSA-m4w9-gch5-c2g4.
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-m4w9-gch5-c2g4 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 377,636 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.
client-certificate-authnpmDescription
Summary
Versions 0.2.1 and 0.3.0 of client-certificate-auth contain an open redirect vulnerability. The middleware unconditionally redirects HTTP requests to HTTPS using the unvalidated Host header, allowing an attacker to redirect users to arbitrary domains.
Vulnerable Code
// lib/clientCertificateAuth.js (versions 0.2.1, 0.3.0)
if (!req.secure && req.header('x-forwarded-proto') != 'https') {
return res.redirect('https://' + req.header('host') + req.url);
}
Attack Scenario
- Attacker crafts a link:
http://vulnerable-app.example.com/login - When victim clicks, attacker intercepts and injects header:
Host: attacker.com - Server responds:
302 Found → https://attacker.com/login - Victim is redirected to attacker-controlled site
Impact
- Phishing: Attackers can use trusted domain links to redirect victims to credential-harvesting pages
- OAuth/SSO Token Theft: In authentication flows, authorization codes or tokens may leak via redirect
- Referer Leakage: Sensitive URL parameters may be exposed to attacker domains via the Referer header
- Cache Poisoning: In deployments with shared caches, malicious redirects may be cached and served to other users
Exploitability
Exploitation requires that HTTP traffic reaches the Node.js application without TLS termination setting x-forwarded-proto: https. This condition is uncommon in production deployments behind modern reverse proxies or load balancers, which limits real-world exploitability.
Fix
The vulnerable redirect behavior has been completely removed in version 1.0.0.
npm install client-certificate-auth@^1.0.0
Workarounds
If upgrading is not immediately possible:
- Block HTTP traffic at the network/load balancer level
- Ensure your reverse proxy always sets
x-forwarded-proto: https - Add middleware before
clientCertificateAuthto validate theHostheader against an allowlist
References
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | client-certificate-auth | ≥ 0.2.1&&< 1.0.0 | 1.0.0npm install client-certificate-auth@1.0.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for client-certificate-auth, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update client-certificate-auth to 1.0.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-m4w9-gch5-c2g4 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-m4w9-gch5-c2g4 can be triaged on real exposure rather than presence alone.
Tailored to GHSA-m4w9-gch5-c2g4. 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-m4w9-gch5-c2g4 in your dependencies?
O3 Security finds GHSA-m4w9-gch5-c2g4 across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.