NGINX Gateway Fabric: Configuration injection via AuthenticationFilter realm
Summary
NGINX Gateway Fabric writes the realm value of a namespaced AuthenticationFilter into the shared nginx.conf without escaping or validation. An authenticated user who can create or change AuthenticationFilter resources can craft a realm value that closes the quoted directive and the enclosing location block, then injects arbitrary NGINX directives into the data-plane configuration of a shared Gateway. According to the vendor record, this can allow reading co-located tenants' mounted secrets, SSRF, reading the pod ServiceAccount token and hijacking other tenants' routes. Exploitation requires valid cluster credentials, so the main risk is internal, mainly in multi-tenant clusters.
Affected
- F5 NGINX Gateway Fabric 2.4.0 up to but excluding 2.8.0 (per CVE record)
- Unknown: whether versions before 2.4.0 are affected
- Unknown: default configuration status
Fixed in
- Upgrade to NGINX Gateway Fabric 2.8.0 (per Bitnami/OSV and VulDB; verify against F5 advisory K000162609)
- Unknown: fixed versions for other release branches
Workaround
- Restrict write access to AuthenticationFilter resources and Secrets to fully trusted administrators via Kubernetes RBAC. The CVE record states this is the only complete mitigation.
- Do not share one Gateway across tenants that do not trust each other.
Exploitation
- CISA SSVC assessment: exploitation none, automatable no, technical impact total.
- No confirmed exploitation in the wild found.
- No public proof of concept found in a limited search.
- VulDB rates exploitability as easy; its 0-Day tag is ambiguous.
Our recommendation
- Check whether NGINX Gateway Fabric versions 2.4.0 to 2.7.x are in use.
- Upgrade to 2.8.0 or later, after confirming the fix in F5 advisory K000162609.
- Until then, restrict who can create or change AuthenticationFilter, Secrets and route resources.
- Do not share Gateways across tenants that do not trust each other.
- Review existing AuthenticationFilter realm values for unusual characters and monitor changes to these resources.
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- F5 advisory K000162609 my.f5.com
- OSV: BIT-nginx-gateway-fabric-2026-91184 osv.dev
- VulDB entry 419931 vuldb.com
- Vulners OSV listing vulners.com
- Offseq threat radar entry radar.offseq.com
- NGINX Gateway Fabric basic authentication documentation docs.nginx.com
Researched and written up in English and German by an AI (Claude by Anthropic) based on NVD, CISA, EPSS and the sources listed. The vendor information is authoritative. Researched on 1 Nov 2026, 04:02.
Original description (NVD)
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.
NVD references (1)
Sources
The tracker combines official, freely usable data sources – updated continuously:
- NVD (NIST) – CVEs, rating (CVSS), affected products
- CISA KEV – vulnerabilities confirmed by CISA as actively exploited
- CISA Vulnrichment – CISA assessment (SSVC) in the official CVE record
- FIRST EPSS – probability of exploitation
- Microsoft MSRC – Patch Tuesday: vulnerabilities, severity, updates
- PoC-in-GitHub – public proof-of-concept repositories
- Metasploit (Rapid7) – modules of the Metasploit Framework
- Exploit-DB (OffSec) – archive of public exploits (links only)
- Patch days: official vendor pages (linked per vendor) (Vendor patch days)
This product uses data from the NVD API but is not endorsed or certified by the NVD. EPSS data © FIRST.org.
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