Authentication Filter Vulnerability in NGINX Gateway Fabric by F5 Networks
CVE-2026-91184

8.7HIGH

Key Information:

Vendor

F5
Status
Nginx Gateway Fabric
Vendor
CVE Published:
14 October 2026

What is CVE-2026-91184?

The NGINX Gateway Fabric has a security vulnerability that allows a namespaced authenticated attacker to manipulate the AuthenticationFilter by injecting unescaped input. This occurs through the spec.basic.realm and spec.jwt.realm fields, which are rendered directly into the NGINX data-plane configuration without proper validation or escaping. By exploiting this flaw, an attacker can close the quoted directive and add arbitrary NGINX directives, leading to potential unauthorized access to sensitive data, SSRF attacks, and hijacking of other tenants' routes. The impact of this vulnerability is confined to the control plane, with no data plane exposure.

Affected Version(s)

NGINX Gateway Fabric 2.4.0 < 2.8.0

References

https://my.f5.com/manage/s/article/K000162609
vendor-advisory

CVSS V4

Score:
8.7
Severity:
HIGH
Confidentiality:
High
Integrity:
High
Availability:
High
Attack Vector:
Network
Attack Complexity:
Low
Attack Required:
None
Privileges Required:
Undefined
User Interaction:
None

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

F5 acknowledges apvxlab (AppViewX security research) for bringing this issue to our attention and following the highest standards of coordinated disclosure.
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