F5 NGINX Ingress Controller up to 5.5.1 Configuration Generator injection

Summaryinfo

A vulnerability, which was classified as very critical, was found in F5 NGINX Ingress Controller up to 5.5.1. The impacted element is an unknown function of the component Configuration Generator. Executing a manipulation can lead to injection. This vulnerability is handled as CVE-2026-55723. The attack can be executed remotely. There is not any exploit available.

Detailsinfo

A vulnerability was found in F5 NGINX Ingress Controller up to 5.5.1. It has been declared as very critical. This vulnerability affects some unknown functionality of the component Configuration Generator. The manipulation with an unknown input leads to a injection vulnerability. The CWE definition for the vulnerability is CWE-74. The product constructs all or part of a command, data structure, or record using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify how it is parsed or interpreted when it is sent to a downstream component. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

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.

The advisory is shared for download at my.f5.com. This vulnerability was named CVE-2026-55723 since 06/18/2026. The exploitation appears to be easy. The attack can be initiated remotely. The exploitation needs additional levels of successful authentication. There are neither technical details nor an exploit publicly available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 07/15/2026). The MITRE ATT&CK project declares the attack technique as T1055.

Upgrading to version 5.5.2 or 2026-lts-r3 eliminates this vulnerability.

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Productinfo

Type

• Web Server

Vendor

• F5

Name

• NGINX Ingress Controller

Version

• 5.5.0
• 5.5.1

License

• commercial

Website

• Vendor: https://f5.com/

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