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CVE-2026-34403

Nginxui Nginx UI vulnerability

8.1 HIGHPublic exploitEPSS 0.22%
  1. Published20 Apr 2026

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.

CVSS 3.1 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredNone
User interactionRequired
ScopeUnchanged
ConfidentialityHigh
IntegrityHigh
AvailabilityNone
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N

Affected products

Nginxui Nginx UI< 2.3.5

Remediation

Fixed in
Nginxui Nginx UI≥ 2.3.5

References

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Frequently asked

Is CVE-2026-34403 being actively exploited?

CVE-2026-34403 is not in the CISA KEV catalog. A public exploit reference exists, so treat it as exploitable. Its EPSS exploit probability is 0.22%.

How severe is CVE-2026-34403?

CVE-2026-34403 has a CVSS 3.1 base score of 8.1, rated high. EPSS estimates a 0.22% probability of exploitation.

Which products are affected by CVE-2026-34403?

Affected products include Nginxui Nginx UI.

How do I fix CVE-2026-34403?

Upgrade affected software to a fixed version, for example Nginxui Nginx UI 2.3.5 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2026-34403 against the real software inventory on every managed device, as each hourly inventory arrives. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.