CyberSecBulletin
CVE-2026-34403NVD status: Analyzed

nginx-ui: Missing Origin Validation in WebSockets

Published Updated By the CyberSecBulletin desk

CVE-2026-34403 is a high-severity missing origin validation in websockets vulnerability in nginx-ui from 0xJacky, with a CVSS 3.1 base score of 8.1 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, but only if a user takes part, for example by opening a link or file. Affected nginx-ui versions: < 2.3.5. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.18% chance of exploitation within 30 days, which is low compared with other CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Check which version of nginx-ui you run against the affected versions below, and install the vendor's latest release.
  2. Read the advisory on github.com for workarounds and exact fixed builds.
  3. Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
  4. Because the attack needs a user to take part, warn users about unexpected links and files related to this product until it is patched.

Affected products and versions

VendorProductAffected versionsFixed in
0xJackynginx-ui< 2.3.5Not stated

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
NetworkCan be exploited remotely over a network, including the internet.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
NoneNo account or login is needed.
User interaction
RequiredA user must take an action such as opening a file or link.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
HighAll data handled by the component can be read.
Integrity
HighData or code can be modified at will.
Availability
NoneAvailability is not affected.

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N. Scored by NVD.

Scoring systemScoreSeverityScored by
CVSS 4.05.5MediumCNA (github.com)
CVSS 3.18.1HighNVD

Official 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.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Missing Origin Validation in WebSockets

The product uses a WebSocket, but it does not properly verify that the source of data or communication is valid.

How developers prevent this class of flaw

  • Enable CORS-like access restrictions by verifying the 'Origin' header during the WebSocket handshake.
  • Use a randomized CSRF token to verify requests.
  • Use TLS to securely communicate using 'wss' (WebSocket Secure) instead of 'ws'.

More Missing Origin Validation in WebSockets vulnerabilities (CWE-1385)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: poc, automatable: no, technical impact: partial).
  3. Record last changed materially (score, affected products, status or references).

References

Patches and release notes

Other vulnerabilities in nginx-ui

All nginx-ui vulnerabilities

Recent Missing Origin Validation in WebSockets vulnerabilities

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