CVE-2026-34403Public exploitNetwork attack vector

Session hijacking via unrestricted WebSocket origins

Published Apr 20, 2026 · Updated Apr 20, 2026

Cross-site WebSocket hijacking in Nginx UI before 2.3.5 allows remote attackers to control authenticated WebSockets through a malicious webpage. Every WebSocket upgrader sets CheckOrigin to return true, while cookie-carried tokens authenticate cross-origin upgrade requests. Exploitation requires a logged-in administrator to visit attacker-controlled content; exposed endpoints permit data reads, administrative actions, and a PTY shell when OTP is disabled.

CVSS severity8.1
High
EPSS probability0.18%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Cross-site WebSocket hijacking in Nginx UI before 2.3.5 allows remote attackers to control authenticated WebSockets through a malicious webpage. Every WebSocket upgrader sets CheckOrigin to return true, while cookie-carried tokens authenticate cross-origin upgrade requests. Exploitation requires a logged-in administrator to visit attacker-controlled content; exposed endpoints permit data reads, administrative actions, and a PTY shell when OTP is disabled.

The record

CVE
CVE-2026-34403
Published
Apr 20, 2026
Updated
Apr 20, 2026
Vendor
0xJacky
Product
Nginx UI
Classifications
CWE-1385, CWE-352, T1189
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 20, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 20, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 2.3.5

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

0xJacky · Nginx UIversion=< 2.3.5

Published CVSS scores

8.1NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N
5.5GitHub, Inc.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
8.6GitHub Advisory DatabaseCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:H/VI:H/VA:H/SC:L/SI:L/SA:L

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-1385Missing Origin Validation in WebSockets
CWE-352Cross-Site Request Forgery (CSRF)
T1189Drive-by Compromise

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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