CVE-2026-55723

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NGINX Ingress Controller Configuration Injection Vulnerability

Publication date: 2026-07-15

Last updated on: 2026-07-16

Assigner: F5 Networks

Description

When NGINX Ingress Controller is configured with Custom Resource Definitions (CRDs) or Ingress annotations, an injection vulnerability exists in the configuration generator of NGINX Ingress Controller. Multiple user-controllable fields are written into the generated NGINX configuration without sanitization. An authenticated attacker with permission to create or modify these CRDs or annotations may craft values that inject arbitrary NGINX configuration directives. Impact: An authenticated attacker granted write access to NGINX Ingress Controller CRDs or Ingress annotations through the Kubernetes API may be able to inject arbitrary NGINX configuration directives, create or delete files, or disable services. 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.

CVSS Scores

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Meta Information

Published

2026-07-15

Last Modified

2026-07-16

Generated

2026-08-04

AI Q&A

2026-07-16

EPSS Evaluated

2026-08-03

NVD

CVE-2026-55723

EUVD

EUVD-2026-44680

Affected Vendors & Products

Vendor	Product	Version / Range
f5	nginx_ingress_controller	From 4.0.0 (inc) to 4.0.1 (inc)
f5	nginx_ingress_controller	From 5.0.0 (inc) to 5.5.2 (exc)
f5	nginx_ingress_controller	From 3.6.0 (inc) to 3.7.2 (inc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-76	The product correctly neutralizes certain special elements, but it improperly neutralizes equivalent special elements.

Attack-Flow Graph

Executive Summary

This vulnerability is an injection flaw in NGINX Ingress Controller when configured with Custom Resource Definitions or Ingress annotations. User-controllable fields are written into the NGINX configuration without proper sanitization, allowing attackers to inject arbitrary NGINX directives.

Detection Guidance

To detect this vulnerability, inspect NGINX Ingress Controller configurations for unauthorized CRDs or annotations. Check for unexpected NGINX directives in generated configs. Review Kubernetes API logs for suspicious modifications to Ingress resources.

Impact Analysis

An authenticated attacker with write access to NGINX Ingress Controller CRDs or annotations could inject malicious NGINX configuration. This may allow them to create or delete files, disable services, or alter NGINX behavior, though data plane exposure is not possible.

Compliance Impact

This is a control plane issue affecting configuration integrity. While not directly exposing data, unauthorized configuration changes could violate compliance by disrupting security controls or logging mechanisms required by standards like GDPR or HIPAA.

Mitigation Strategies

Review and restrict write access to NGINX Ingress Controller CRDs or Ingress annotations in Kubernetes. Ensure only trusted users have permissions to modify these configurations. Update to a patched version if available.

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