CVE-2026-84321

Received Received - Intake

Stored XSS in Nginx UI via Short Token Cache

Publication date: 2026-10-12

Last updated on: 2026-10-12

Assigner: GitHub, Inc.

Description

Nginx UI is a web user interface for the Nginx web server. Prior to 2.4.1, GenerateShortToken creates standalone short-token records without a long Token value, but DeleteUserTokens invalidates cached entries only when the long Token field is nonempty. A revoked short token can therefore remain in the short_token cache and authenticate again if the associated account is re-enabled before the cache entry expires because GetTokenUserByShortToken reads the surviving entry, restoring access to HTTP or WebSocket routes that accept short-token authentication. This issue is fixed in version 2.4.1.

CVSS Scores

EPSS Scores

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Meta Information

Published

2026-10-12

Last Modified

2026-10-12

Generated

2026-10-13

AI Q&A

2026-10-13

EPSS Evaluated

N/A

NVD

CVE-2026-84321

Affected Vendors & Products

Vendor	Product	Version / Range
0xJacky	nginx-ui	< 2.4.1

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-613	According to WASC, "Insufficient Session Expiration is when a web site permits an attacker to reuse old session credentials or session IDs for authorization."

Attack-Flow Graph

Executive Summary

Nginx UI before version 2.4.1 has a flaw in token handling. When a user's account is disabled and re-enabled, a revoked short token can remain active in the cache. This happens because the system only invalidates cached tokens when a long token exists, but short tokens are created without one. The cached short token can still authenticate access to protected routes.

Detection Guidance

Check if your Nginx UI version is below 2.4.1. Inspect logs for unusual short-token authentication attempts or cached entries persisting after account revocation. No specific commands are provided in the context.

Impact Analysis

If you use Nginx UI versions before 2.4.1, an attacker could exploit this to regain access to your account or services even after your account was disabled. This could lead to unauthorized access to sensitive data or system functions, depending on the permissions of the compromised account.

Compliance Impact

This vulnerability could lead to unauthorized access, which may violate data protection requirements under GDPR or HIPAA. If sensitive data is exposed due to this flaw, organizations could face compliance violations, legal penalties, or reputational damage.

Mitigation Strategies

Upgrade Nginx UI to version 2.4.1 or later. Review and clear any cached short tokens. Disable and re-enable affected accounts to invalidate cached entries.

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