CVE-2026-55723 nginx ingress controller vulnerability
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.
Quick answer
f5 nginx ingress controller should be reviewed and updated if it matches the affected versions. The recommended fix is to apply the vendor-supported patched version or the mitigation steps below, then retest the public website with Fixnx.
Who is affected
Affected versions
- Review vendor advisory for affected versions.
Fixed versions
- Apply the latest vendor-supported patched version.
How to fix it
CVE-2026-55723 affects f5 nginx ingress controller and is rated high. 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. Fix this first on internet-facing or admin systems. The practical fix is to upgrade to the latest vendor-supported patched release listed in the advisory, then verify the system is no longer exposed.
- Inventory every server, container, appliance, cluster, plugin, or device that uses f5 nginx ingress controller.
- Check the installed version and configuration against CVE-2026-55723 and the linked advisory.
- Apply the vendor fix: upgrade to the latest vendor-supported patched release listed in the advisory.
- Limit Kubernetes RBAC so only trusted admins can edit Ingress, TransportServer, CRD, and annotation values.
- Disable or isolate the affected feature if you cannot update right away.
- Review Kubernetes audit logs and controller logs for malformed resource updates or crash loops.
- Rotate secrets, rebuild affected systems, or reset sessions if you suspect compromise.
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Verify the fix
- Confirm f5 nginx ingress controller is running the patched version or the approved mitigation is active.
- Confirm affected public, admin, API, tunnel, or cluster access is limited to trusted users.
- Repeat the risky workflow or a safe test case and confirm the issue no longer appears.
- Review logs again after the fix for crashes, bypass attempts, file access, or suspicious changes.
- Save version, config, log, and scan evidence for your remediation record.
Related categories
Trusted references
FAQ
What is affected by CVE-2026-55723?
f5 nginx ingress controller should be checked against the vendor advisory and trusted references linked on this page.
What should I fix first?
Start with internet-facing sites, admin panels, login flows, plugins, themes, modules, packages, and systems that process user-controlled input or sensitive data.
How do I confirm the fix worked?
Apply the patched version or mitigation, clear caches where relevant, retest the affected workflow, and run a new Fixnx scan to verify public website exposure signals.
How are Fixnx security risk categories chosen?
Fixnx keeps one canonical risk page and assigns only broad, relevant categories such as ecosystem, technology area, or vulnerability class.