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GHSA-m4w9-gch5-c2g4

MediumCVSS 6.1 / 10
Published Feb 6, 2026·Last modified Feb 6, 2026
Affected Components(0)

No affected components available

Description

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

  1. Attacker crafts a link: http://vulnerable-app.example.com/login
  2. When victim clicks, attacker intercepts and injects header: Host: attacker.com
  3. Server responds: 302 Found → https://attacker.com/login
  4. 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:

  1. Block HTTP traffic at the network/load balancer level
  2. Ensure your reverse proxy always sets x-forwarded-proto: https
  3. Add middleware before clientCertificateAuth to validate the Host header against an allowlist

References

Risk Scores
Base Score
6.1

The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. The attacker needs the user to perform some action, like clicking a link. The vulnerability can affect other systems as well, not just the initial system. There is a low impact on the confidentiality of the information. There is a low impact on the integrity of the data.

Threat Intelligence
5.6

Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.

EPSS
0.17%

The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.

Exploit
Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

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