Vulnerability-Lookup

CVE-2026-81868 (GCVE-0-2026-81868)

Vulnerability from cvelistv5 – Published: 2026-09-17 15:36 – Updated: 2026-09-17 15:36

Title

Steeltoe: Header-forwarded client cert lacks proof of private-key possession

Summary

Steeltoe is an open source project that provides a collection of libraries that helps users build cloud-native applications. Prior to 4.3.0, Steeltoe.Security.Authorization.Certificate deployments using AddOrgAndSpacePolicies() and UseCertificateAuthorization() trust the public certificate supplied in the X-Client-Cert request header without proving possession of the corresponding private key. Common Cloud Foundry routers do not remove this header from inbound requests. When inbound requests are not restricted to a known trusted proxy source IP, an attacker who obtains the public certificate of an application instance in the target organization or space and can reach the application can spoof X-Client-Cert to bypass the SameOrg and SameSpace policies for the certificate validity period. This issue is fixed in version 4.3.0.

Severity

6.5 (Medium)


                        
                          CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:N

CWE

CWE-288 - Authentication Bypass Using an Alternate Path or Channel
CWE-295 - Improper Certificate Validation

Assigner

GitHub_M mitre root

References

3 references

URL	Tags
https://github.com/SteeltoeOSS/security-advisorie…	x_refsource_CONFIRM
https://github.com/SteeltoeOSS/Steeltoe/commit/b6…	x_refsource_MISC
https://github.com/SteeltoeOSS/Steeltoe/releases/…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version	CPE status
SteeltoeOSS	security-advisories	Affected: < 4.3.0	guessed

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "cna": {
      "affected": [
        {
          "product": "security-advisories",
          "vendor": "SteeltoeOSS",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 4.3.0"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "Steeltoe is an open source project that provides a collection of libraries that helps users build cloud-native applications. Prior to 4.3.0, Steeltoe.Security.Authorization.Certificate deployments using AddOrgAndSpacePolicies() and UseCertificateAuthorization() trust the public certificate supplied in the X-Client-Cert request header without proving possession of the corresponding private key. Common Cloud Foundry routers do not remove this header from inbound requests. When inbound requests are not restricted to a known trusted proxy source IP, an attacker who obtains the public certificate of an application instance in the target organization or space and can reach the application can spoof X-Client-Cert to bypass the SameOrg and SameSpace policies for the certificate validity period. This issue is fixed in version 4.3.0."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "HIGH",
            "attackVector": "NETWORK",
            "availabilityImpact": "NONE",
            "baseScore": 6.5,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "HIGH",
            "integrityImpact": "LOW",
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            "version": "3.1"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-288",
              "description": "CWE-288: Authentication Bypass Using an Alternate Path or Channel",
              "lang": "en",
              "type": "CWE"
            }
          ]
        },
        {
          "descriptions": [
            {
              "cweId": "CWE-295",
              "description": "CWE-295: Improper Certificate Validation",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-17T15:36:23.149Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/SteeltoeOSS/security-advisories/security/advisories/GHSA-5mq7-rwhj-4fh9",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/SteeltoeOSS/security-advisories/security/advisories/GHSA-5mq7-rwhj-4fh9"
        },
        {
          "name": "https://github.com/SteeltoeOSS/Steeltoe/commit/b626ef3d60aaf19c68eeeed5ee81045406c8c6d0",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/SteeltoeOSS/Steeltoe/commit/b626ef3d60aaf19c68eeeed5ee81045406c8c6d0"
        },
        {
          "name": "https://github.com/SteeltoeOSS/Steeltoe/releases/tag/4.3.0",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/SteeltoeOSS/Steeltoe/releases/tag/4.3.0"
        }
      ],
      "source": {
        "advisory": "GHSA-5mq7-rwhj-4fh9",
        "discovery": "UNKNOWN"
      },
      "title": "Steeltoe: Header-forwarded client cert lacks proof of private-key possession"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-81868",
    "datePublished": "2026-09-17T15:36:23.149Z",
    "dateReserved": "2026-08-27T17:48:42.118Z",
    "dateUpdated": "2026-09-17T15:36:23.149Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-81868",
      "date": "2026-09-18",
      "epss": "0.00159",
      "percentile": "0.0554"
    },
    "nvd": {
      "cve": {
        "affected": [
          {
            "affectedData": [
              {
                "product": "security-advisories",
                "vendor": "SteeltoeOSS",
                "versions": [
                  {
                    "status": "affected",
                    "version": "\u003c 4.3.0"
                  }
                ]
              }
            ],
            "source": "security-advisories@github.com"
          }
        ],
        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "Steeltoe is an open source project that provides a collection of libraries that helps users build cloud-native applications. Prior to 4.3.0, Steeltoe.Security.Authorization.Certificate deployments using AddOrgAndSpacePolicies() and UseCertificateAuthorization() trust the public certificate supplied in the X-Client-Cert request header without proving possession of the corresponding private key. Common Cloud Foundry routers do not remove this header from inbound requests. When inbound requests are not restricted to a known trusted proxy source IP, an attacker who obtains the public certificate of an application instance in the target organization or space and can reach the application can spoof X-Client-Cert to bypass the SameOrg and SameSpace policies for the certificate validity period. This issue is fixed in version 4.3.0."
          }
        ],
        "id": "CVE-2026-81868",
        "lastModified": "2026-09-17T16:17:47.607",
        "metrics": {
          "cvssMetricV31": [
            {
              "cvssData": {
                "attackComplexity": "HIGH",
                "attackVector": "NETWORK",
                "availabilityImpact": "NONE",
                "baseScore": 6.5,
                "baseSeverity": "MEDIUM",
                "confidentialityImpact": "HIGH",
                "integrityImpact": "LOW",
                "privilegesRequired": "NONE",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:N",
                "version": "3.1"
              },
              "exploitabilityScore": 2.2,
              "impactScore": 4.2,
              "source": "security-advisories@github.com",
              "type": "Secondary"
            }
          ]
        },
        "published": "2026-09-17T16:17:47.607",
        "references": [
          {
            "source": "security-advisories@github.com",
            "url": "https://github.com/SteeltoeOSS/Steeltoe/commit/b626ef3d60aaf19c68eeeed5ee81045406c8c6d0"
          },
          {
            "source": "security-advisories@github.com",
            "url": "https://github.com/SteeltoeOSS/Steeltoe/releases/tag/4.3.0"
          },
          {
            "source": "security-advisories@github.com",
            "url": "https://github.com/SteeltoeOSS/security-advisories/security/advisories/GHSA-5mq7-rwhj-4fh9"
          }
        ],
        "sourceIdentifier": "security-advisories@github.com",
        "vulnStatus": "Received",
        "weaknesses": [
          {
            "description": [
              {
                "lang": "en",
                "value": "CWE-288"
              },
              {
                "lang": "en",
                "value": "CWE-295"
              }
            ],
            "source": "security-advisories@github.com",
            "type": "Primary"
          }
        ]
      }
    }
  }
}

FKIE_CVE-2026-81868

Vulnerability from fkie_nvd - Published: 2026-09-17 16:17 - Updated: 2026-09-17 16:17

Severity

6.5 (Medium) - CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:N

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/SteeltoeOSS/Steeltoe/commit/b626ef3d60aaf19c68eeeed5ee81045406c8c6d0
	security-advisories@github.com	https://github.com/SteeltoeOSS/Steeltoe/releases/tag/4.3.0
	security-advisories@github.com	https://github.com/SteeltoeOSS/security-advisories/security/advisories/GHSA-5mq7-rwhj-4fh9

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "product": "security-advisories",
          "vendor": "SteeltoeOSS",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 4.3.0"
            }
          ]
        }
      ],
      "source": "security-advisories@github.com"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "Steeltoe is an open source project that provides a collection of libraries that helps users build cloud-native applications. Prior to 4.3.0, Steeltoe.Security.Authorization.Certificate deployments using AddOrgAndSpacePolicies() and UseCertificateAuthorization() trust the public certificate supplied in the X-Client-Cert request header without proving possession of the corresponding private key. Common Cloud Foundry routers do not remove this header from inbound requests. When inbound requests are not restricted to a known trusted proxy source IP, an attacker who obtains the public certificate of an application instance in the target organization or space and can reach the application can spoof X-Client-Cert to bypass the SameOrg and SameSpace policies for the certificate validity period. This issue is fixed in version 4.3.0."
    }
  ],
  "id": "CVE-2026-81868",
  "lastModified": "2026-09-17T16:17:47.607",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "HIGH",
          "attackVector": "NETWORK",
          "availabilityImpact": "NONE",
          "baseScore": 6.5,
          "baseSeverity": "MEDIUM",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "LOW",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:N",
          "version": "3.1"
        },
        "exploitabilityScore": 2.2,
        "impactScore": 4.2,
        "source": "security-advisories@github.com",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-09-17T16:17:47.607",
  "references": [
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/SteeltoeOSS/Steeltoe/commit/b626ef3d60aaf19c68eeeed5ee81045406c8c6d0"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/SteeltoeOSS/Steeltoe/releases/tag/4.3.0"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/SteeltoeOSS/security-advisories/security/advisories/GHSA-5mq7-rwhj-4fh9"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Received",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-288"
        },
        {
          "lang": "en",
          "value": "CWE-295"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Primary"
    }
  ]
}

GHSA-5MQ7-RWHJ-4FH9

Vulnerability from github – Published: 2026-09-17 20:30 – Updated: 2026-09-17 20:30

Summary

Steeltoe: Header-forwarded client cert lacks proof of private-key possession

Details

Summary

When Steeltoe's certificate-based authorization (UseCertificateAuthorization) is configured, the default configuration of the middleware relies on the X-Client-Cert HTTP header to identify the client certificate, without verifying private-key possession. This header is not stripped by common Cloud Foundry routers (like Gorouter or Envoy) on inbound requests.

Impact

An attacker who obtains the public certificate of an application instance in the target organization or space can spoof the X-Client-Cert header. This allows the attacker to bypass SameOrg and SameSpace authorization policies, granting unauthorized access to protected endpoints for the duration of the certificate's validity period.

Affected configuration

The application uses AddOrgAndSpacePolicies() and UseCertificateAuthorization() for inter-service authorization.
Inbound requests are not restricted to a known trusted proxy source IP.
The application's endpoints are network-accessible to the attacker (e.g., exposed to the internet via a public Cloud Foundry route, or the attacker has access to the internal Cloud Foundry network).

Mitigations

If an immediate upgrade to a patched version is not possible:

Restrict UseCertificateForwarding to trusted proxy source IPs using ForwardedHeadersOptions.KnownProxies and KnownNetworks.
Change the forwarding header to X-Forwarded-Client-Cert so that Cloud Foundry Gorouter and Envoy header stripping mechanisms apply to inbound untrusted requests.
Add a secondary authorization layer (e.g., a shared secret or mutual TLS at the proxy layer) for sensitive endpoints.
Ensure the application is not bound to a public route unless explicitly required. Use Cloud Foundry internal routes (e.g., .apps.internal) and container-to-container network policies to strictly limit network access to intended internal clients.

Severity

6.5 (Medium)


                  
                    CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:N

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 4.2.0"
      },
      "package": {
        "ecosystem": "NuGet",
        "name": "Steeltoe.Security.Authorization.Certificate"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "4.3.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-81868"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-288",
      "CWE-295"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-09-17T20:30:58Z",
    "nvd_published_at": "2026-09-17T16:17:47Z",
    "severity": "MODERATE"
  },
  "details": "### Summary\n\nWhen Steeltoe\u0027s certificate-based authorization (`UseCertificateAuthorization`) is configured, the default configuration of the middleware relies on the `X-Client-Cert` HTTP header to identify the client certificate, without verifying private-key possession. This header is not stripped by common Cloud Foundry routers (like Gorouter or Envoy) on inbound requests.\n\n### Impact\n\nAn attacker who obtains the public certificate of an application instance in the target organization or space can spoof the `X-Client-Cert` header. This allows the attacker to bypass `SameOrg` and `SameSpace` authorization policies, granting unauthorized access to protected endpoints for the duration of the certificate\u0027s validity period.\n\n### Affected configuration\n\n- The application uses `AddOrgAndSpacePolicies()` and `UseCertificateAuthorization()` for inter-service authorization.\n- Inbound requests are not restricted to a known trusted proxy source IP.\n- The application\u0027s endpoints are network-accessible to the attacker (e.g., exposed to the internet via a public Cloud Foundry route, or the attacker has access to the internal Cloud Foundry network).\n\n### Mitigations\n\nIf an immediate upgrade to a patched version is not possible:\n\n- Restrict `UseCertificateForwarding` to trusted proxy source IPs using `ForwardedHeadersOptions.KnownProxies` and `KnownNetworks`.\n- Change the forwarding header to `X-Forwarded-Client-Cert` so that Cloud Foundry Gorouter and Envoy header stripping mechanisms apply to inbound untrusted requests.\n- Add a secondary authorization layer (e.g., a shared secret or mutual TLS at the proxy layer) for sensitive endpoints.\n- Ensure the application is not bound to a public route unless explicitly required. Use Cloud Foundry internal routes (e.g., `.apps.internal`) and container-to-container network policies to strictly limit network access to intended internal clients.",
  "id": "GHSA-5mq7-rwhj-4fh9",
  "modified": "2026-09-17T20:30:58Z",
  "published": "2026-09-17T20:30:58Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/SteeltoeOSS/security-advisories/security/advisories/GHSA-5mq7-rwhj-4fh9"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-81868"
    },
    {
      "type": "WEB",
      "url": "https://github.com/SteeltoeOSS/Steeltoe/commit/b626ef3d60aaf19c68eeeed5ee81045406c8c6d0"
    },
    {
      "type": "WEB",
      "url": "https://github.com/SteeltoeOSS/Steeltoe/releases/tag/4.3.0"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/SteeltoeOSS/security-advisories"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Steeltoe: Header-forwarded client cert lacks proof of private-key possession"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.

Action not permitted

CVE-2026-81868 (GCVE-0-2026-81868)

FKIE_CVE-2026-81868

GHSA-5MQ7-RWHJ-4FH9

Summary

Impact

Affected configuration

Mitigations

Tags

Sightings

Nomenclature

Related by attack behaviour