CVE-2026-34403: Nginx-UI: Cross-Site WebSocket Hijacking (CSWSH) via missing origin validation on all WebSocket endpoints

CVE-2026-34403 · Severity: high · CVSS 8.1 · Published 2026-04-20

Nginx UI is a web user interface for the Nginx web server. Prior to version 2.3.5, all WebSocket endpoints in nginx-ui use a gorilla/websocket Upgrader with CheckOrigin unconditionally returning true, allowing Cross-Site WebSocket Hijacking (CSWSH). Combined with the fact that authentication tokens are stored in browser cookies (set via JavaScript without HttpOnly or explicit SameSite attributes), a malicious webpage can establish authenticated WebSocket connections to the nginx-ui instance when a logged-in administrator visits the attacker-controlled page. Version 2.3.5 patches the issue.

Technologies: github.com/0xJacky/Nginx-UI (Go), Nginxui Nginx Ui. Vendors: Go, Nginxui.

Quick answers

Is CVE-2026-34403 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-34403 being exploited in the wild.
How severe is CVE-2026-34403?
High severity, with a CVSS score of 8.1, published 20 April 2026.
Which products and versions are affected?
github.com/0xJacky/Nginx-UI (Go) SEMVER:introduced=0,fixed=1.9.10-0.20260316053337-1a9cd29a3082.
Is there a fix for CVE-2026-34403?
Yes. github.com/0xJacky/Nginx-UI (Go): upgrade to 1.9.10-0.20260316053337-1a9cd29a3082 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
Am I affected by CVE-2026-34403?
Check whether you run github.com/0xJacky/Nginx-UI (Go) or Nginxui Nginx Ui at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • github.com/0xJacky/Nginx-UI (Go): upgrade to 1.9.10-0.20260316053337-1a9cd29a3082 or later
    go get github.com/0xJacky/Nginx-UI@v1.9.10-0.20260316053337-1a9cd29a3082

Affected products

  • github.com/0xJacky/Nginx-UI (Go) SEMVER:introduced=0,fixed=1.9.10-0.20260316053337-1a9cd29a3082
  • Nginxui Nginx Ui

Identifiers

  • CVE-2026-34403
  • GHSA-78mf-482w-62qj
  • GO-2026-5210

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