Is CVE-2026-34403 in the CISA KEV catalog?

No. CVE-2026-34403 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2026-34403?

CVE-2026-34403 has a CVSS v3 base score of 8.1 (HIGH).

What is the EPSS score for CVE-2026-34403?

CVE-2026-34403 has an EPSS score of 0.18% (7th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2026-34403?

Upgrade nginx ui to 2.3.5 or later.

CVE & CISA-KEV Catalog

CVE-2026-34403

HIGH

8.1

CVSS v3

NVD

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.

CWE-1385

How to fix

Remediation Available

nginx uiNVD

Affected:< 2.3.5Fixed in:2.3.5CVE-2026-34403derived from NVD

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

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionRequired

ScopeUnchanged

Impact

ConfidentialityHigh

IntegrityHigh

AvailabilityNone

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N

Exploit Intelligence

0.18%probability of exploitation in 30 days

7thpercentile

Low risk: more likely to be exploited than 7% of all known CVEs.

References

Exploit1

github.com

Release Notes1

github.com

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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.