CVE-2026-34403
HIGHDescription
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.
How to fix
TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works
Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.
CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N
Exploit Intelligence
Low risk: more likely to be exploited than 7% of all known CVEs.
References
Related Vulnerabilities
Other CWE-1385 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2024-48849 | Critical | 9.4 | 0.9% | - | - |
| CVE-2025-24964 | Critical | 9.6 | 0.7% | - | Fix |
| CVE-2025-68930 | High | 7.1 | 0.5% | - | - |
| CVE-2023-0957 | High | 8.2 | 0.4% | - | Fix |
| CVE-2024-23168 | Critical | 9.8 | 0.4% | - | - |
| CVE-2014-125071 | Medium | 5.5 | 0.4% | - | Fix |
Common questions
How do I fix CVE-2026-34403?
Upgrade nginx ui to 2.3.5 or later.
Is CVE-2026-34403 being actively exploited?
Not that we know of. CVE-2026-34403 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.18% is the estimated probability that it will be exploited in the next 30 days. That is higher than 7% of all scored CVEs.
How severe is CVE-2026-34403?
CVE-2026-34403 has a CVSS v3 base score of 8.1, rated high. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
What does CVE-2026-34403 affect?
Published advisories record a fix for nginx ui (NVD). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.
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Markdown
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-04-22.