---
id: CVE-2026-91184
title: "Description\n\nNGINX Gateway Fabric\_has a vulnerability when it renders the spec.basic.realm (and spec.jwt.realm) field of a namespaced AuthenticationFilter verbatim, unescaped and unvalidated, into the shared data-plane nginx.conf as auth…"
summary: "Description\n\nNGINX Gateway Fabric\_has a vulnerability when it renders the spec.basic.realm (and spec.jwt.realm) field of a namespaced AuthenticationFilter verbatim, unescaped and unvalidated, into the shared data-plane nginx.conf as auth…"
severity: high
cvss: 8.8
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H'
cwe:
  - CWE-76
published: '2026-10-14'
updated: '2026-10-14'
sourceUpdated: '2026-10-14T16:04:11.750'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-91184'
references:
  - url: 'https://my.f5.com/manage/s/article/K000162609'
    label: f5sirt@f5.com
tags:
  - nvd
ingestedAt: '2026-10-14T15:36:14.033Z'
---

## Overview

Description

NGINX Gateway Fabric has a vulnerability when it renders the spec.basic.realm (and spec.jwt.realm) field of a namespaced AuthenticationFilter verbatim, unescaped and unvalidated, into the shared data-plane nginx.conf as auth_basic "<realm>";. A namespaced authenticated attacker that configures AuthenticationFilter CRD to an HTTPRoute/GRPCRoute on a shared Gateway can craft a realm value that closes the quoted directive and the enclosing location {} block and injects arbitrary NGINX directives into that Gateway's data-plane config. 

Impact

A remote authenticated attacker can send crafted requests to configure NGINX Gateway Fabric AuthenticationFilter CRD and may be able to read every co-located tenant's mounted secrets, SSRF via proxy_pass, reading the pod ServiceAccount token, or hijacking other tenants' routes. There is no data plane exposure; this is a control plane issue only.






Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.