CVE-2026-91184
HighCVSS 8.8Exploitation Probability (EPSS)
Low risk40th percentile - higher than 40% of all known CVEs
Summary
Vulnerability in NGINX Gateway Fabric where the spec.basic.realm (and spec.jwt.realm) field of a namespaced AuthenticationFilter is rendered verbatim, unescaped and unvalidated, into the shared data-plane nginx.conf as auth_basic "<realm>";. An authenticated attacker with namespace access can inject arbitrary NGINX directives into the Gateway's data-plane config.
Risk Assessment
An authenticated attacker can read every co-located tenant's mounted secrets, perform SSRF via proxy_pass, read the pod ServiceAccount token, or hijack other tenants' routes. This is a control plane issue only; no data plane exposure.
Recommendation
Upgrade NGINX Gateway Fabric to a patched version. Restrict access to AuthenticationFilter configuration to trusted users only.
Other vulnerabilities in NGINX Gateway Fabric
See all- CVE-2026-96615Medium
NGINX Gateway Fabric configured with the Gateway CRD and an authenticated gRPC connection with NGINX Agent allows a namespaced authenticated attacker with access to a service account to impersonate the authenticated NGINX Agent gRPC connection and read TLS private keys of Gateway deployments in another namespace.
- CVE-2026-66362High
A vulnerability in NGINX Gateway Fabric where user-supplied string values from the Authentication Filter Custom Resource Definition clientID or cookieName fields, or in the clientSecret field of a Secret, are rendered directly into NGINX configuration templates without sanitization or escaping.
- CVE-2026-50107High
In NGINX Plus or NGINX Open Source configured as the data plane for NGINX Gateway Fabric, an injection vulnerability exists in the NGINX configuration generator component. User-supplied string values from the NginxProxy Custom Resource Definition access log format setting are rendered without sanitization, allowing for the injection of arbitrary NGINX configuration directives.
- CVE-2026-32682Medium
A vulnerability in NGINX Gateway Fabric allows an authenticated remote attacker with permission to create or modify GRPCRoute resources to cause the control plane to terminate by sending specially crafted GRPCRoute configurations containing backendRef filters.
- CVE-2026-11311High
In NGINX Gateway Fabric, when NGINX Plus is configured as the data plane, an injection vulnerability exists in the NGINX configuration generator component. User-supplied string values from the serverTokens field of the NginxProxy Custom Resource Definition and the extraAuthArgs field of the AuthenticationFilter Custom Resource Definition are rendered directly into NGINX configuration templates without sanitization or escaping. An authenticated attacker with permission to create or modify these Custom Resource Definitions may inject arbitrary NGINX configuration directives.
Original NVD description (English source)
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.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS