Common Weakness Enumeration

CWE-76

Improper Neutralization of Equivalent Special Elements

The product correctly neutralizes certain special elements, but it improperly neutralizes equivalent special elements.

CVE-2026-55723 (GCVE-0-2026-55723)

Vulnerability from cvelistv5 – Published: 2026-07-15 14:33 – Updated: 2026-07-16 03:55
VLAI
Title
NGINX Ingress Controller vulnerability
Summary
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.
SSVC
Exploitation: none Automatable: no Technical Impact: total
CISA Coordinator (v2.0.3)
CWE
  • CWE-76 - Improper Neutralization of Equivalent Special Elements
Assigner
f5
References
URL Tags
https://my.f5.com/manage/s/article/K000161800 vendor-advisorypatch
Impacted products
Vendor Product Version
F5 NGINX Ingress Controller Affected: 5.0.0 , < 5.5.2 (custom)
Affected: 2026-lts-r1 , < 2026-lts-r3 (custom)
Create a notification for this product.
Date Public
2026-07-15 14:00
Credits
F5
Show details on NVD website

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-55723",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "total"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-07-15T00:00:00+00:00",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-07-16T03:55:31.898Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "defaultStatus": "unknown",
          "modules": [
            "Custom Resource Definitions",
            "Ingress Annotations"
          ],
          "product": "NGINX Ingress Controller",
          "vendor": "F5",
          "versions": [
            {
              "lessThan": "5.5.2",
              "status": "affected",
              "version": "5.0.0",
              "versionType": "custom"
            },
            {
              "lessThan": "2026-lts-r3",
              "status": "affected",
              "version": "2026-lts-r1",
              "versionType": "custom"
            }
          ]
        }
      ],
      "credits": [
        {
          "lang": "en",
          "type": "finder",
          "value": "F5"
        }
      ],
      "datePublic": "2026-07-15T14:00:00.000Z",
      "descriptions": [
        {
          "lang": "en",
          "supportingMedia": [
            {
              "base64": false,
              "type": "text/html",
              "value": "\u003cspan style=\"background-color: rgb(255, 255, 255);\"\u003eWhen 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.\u003c/span\u003e \u003cbr\u003e\u003cbr\u003eImpact:\u003cbr\u003eAn 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.\u003cbr\u003e\u003cbr\u003eNote: Software versions which have reached End of Technical Support (EoTS) are not evaluated."
            }
          ],
          "value": "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. \n\nImpact:\nAn 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.\n\nNote: Software versions which have reached End of Technical Support (EoTS) are not evaluated."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "LOW",
            "baseScore": 8.3,
            "baseSeverity": "HIGH",
            "confidentialityImpact": "HIGH",
            "integrityImpact": "HIGH",
            "privilegesRequired": "LOW",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:L",
            "version": "3.1"
          },
          "format": "CVSS",
          "scenarios": [
            {
              "lang": "en",
              "value": "GENERAL"
            }
          ]
        },
        {
          "cvssV4_0": {
            "Automatable": "NOT_DEFINED",
            "Recovery": "NOT_DEFINED",
            "Safety": "NOT_DEFINED",
            "attackComplexity": "LOW",
            "attackRequirements": "NONE",
            "attackVector": "NETWORK",
            "baseScore": 8.7,
            "baseSeverity": "HIGH",
            "privilegesRequired": "LOW",
            "providerUrgency": "NOT_DEFINED",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "NONE",
            "subIntegrityImpact": "NONE",
            "userInteraction": "NONE",
            "valueDensity": "NOT_DEFINED",
            "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:L/SC:N/SI:N/SA:N",
            "version": "4.0",
            "vulnAvailabilityImpact": "LOW",
            "vulnConfidentialityImpact": "HIGH",
            "vulnIntegrityImpact": "HIGH",
            "vulnerabilityResponseEffort": "NOT_DEFINED"
          },
          "format": "CVSS",
          "scenarios": [
            {
              "lang": "en",
              "value": "GENERAL"
            }
          ]
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-76",
              "description": "CWE-76 Improper Neutralization of Equivalent Special Elements",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-07-15T14:33:44.806Z",
        "orgId": "9dacffd4-cb11-413f-8451-fbbfd4ddc0ab",
        "shortName": "f5"
      },
      "references": [
        {
          "tags": [
            "vendor-advisory",
            "patch"
          ],
          "url": "https://my.f5.com/manage/s/article/K000161800"
        }
      ],
      "source": {
        "discovery": "INTERNAL"
      },
      "title": "NGINX Ingress Controller vulnerability",
      "x_generator": {
        "engine": "F5 SIRTBot v1.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "9dacffd4-cb11-413f-8451-fbbfd4ddc0ab",
    "assignerShortName": "f5",
    "cveId": "CVE-2026-55723",
    "datePublished": "2026-07-15T14:33:44.806Z",
    "dateReserved": "2026-06-17T23:45:50.277Z",
    "dateUpdated": "2026-07-16T03:55:31.898Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}










Mitigation

Phase: Requirements

Description:

  • Programming languages and supporting technologies might be chosen which are not subject to these issues.
Mitigation

Phase: Implementation

Description:

  • Utilize an appropriate mix of allowlist and denylist parsing to filter equivalent special element syntax from all input.

No CAPEC attack patterns related to this CWE.

Back to CWE stats page