Vulnerability-Lookup

FKIE_CVE-2026-81315

Vulnerability from fkie_nvd - Published: 2026-08-31 01:16 - Updated: 2026-09-01 21:15

Severity

7.4 (High) - CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

Summary

Origin Validation Error vulnerability in ash-project ash_ai allows a malicious web page to bypass the MCP server's DNS-rebinding protection and issue cross-site requests to a user's local MCP server with that user's actor. In AshAi.Mcp.Server, with the default allowed_origins: nil, origin_allowed?/3 accepts an origin when uri.host == conn.host and the forwarded scheme is https. Both values are attacker-controlled: conn.host comes from the Host header and the scheme is read from the raw x-forwarded-proto header with no trusted-proxy check. Under DNS rebinding the browser sends the attacker's origin and a matching host, and page JavaScript may set X-Forwarded-Proto: https, so the check passes with no TLS or proxy involved. The fix trusts only localhost origins by default; other origins require an explicit allowed_origins allowlist. This issue affects ash_ai: from 0.8.0 before 1.0.0.

References

	URL	Tags
	6b3ad84c-e1a6-4bf7-a703-f496b71e49db	https://cna.erlef.org/cves/CVE-2026-81315.html
	6b3ad84c-e1a6-4bf7-a703-f496b71e49db	https://github.com/ash-project/ash_ai/commit/28af68d73134df0b8fb3aa6ab03e8fd795b07c21
	6b3ad84c-e1a6-4bf7-a703-f496b71e49db	https://github.com/ash-project/ash_ai/security/advisories/GHSA-c92r-f3rr-q49h
	6b3ad84c-e1a6-4bf7-a703-f496b71e49db	https://osv.dev/vulnerability/EEF-CVE-2026-81315
	134c704f-9b21-4f2e-91b3-4a467353bcc0	https://github.com/ash-project/ash_ai/security/advisories/GHSA-c92r-f3rr-q49h

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "collectionURL": "https://repo.hex.pm",
          "cpes": [
            "cpe:2.3:a:ash-project:ash_ai:*:*:*:*:*:*:*:*"
          ],
          "defaultStatus": "unaffected",
          "modules": [
            "\u0027Elixir.AshAi.Mcp.Server\u0027"
          ],
          "packageName": "ash_ai",
          "packageURL": "pkg:hex/ash_ai",
          "product": "ash_ai",
          "programFiles": [
            "lib/ash_ai/mcp/server.ex"
          ],
          "programRoutines": [
            {
              "name": "\u0027Elixir.AshAi.Mcp.Server\u0027:check_origin/2"
            },
            {
              "name": "\u0027Elixir.AshAi.Mcp.Server\u0027:origin_allowed?/3"
            }
          ],
          "repo": "https://github.com/ash-project/ash_ai",
          "vendor": "ash-project",
          "versions": [
            {
              "lessThan": "1.0.0",
              "status": "affected",
              "version": "0.8.0",
              "versionType": "semver"
            }
          ]
        },
        {
          "collectionURL": "https://github.com",
          "cpes": [
            "cpe:2.3:a:ash-project:ash_ai:*:*:*:*:*:*:*:*"
          ],
          "defaultStatus": "unaffected",
          "modules": [
            "\u0027Elixir.AshAi.Mcp.Server\u0027"
          ],
          "packageName": "ash-project/ash_ai",
          "packageURL": "pkg:github/ash-project/ash_ai",
          "product": "ash_ai",
          "programFiles": [
            "lib/ash_ai/mcp/server.ex"
          ],
          "programRoutines": [
            {
              "name": "\u0027Elixir.AshAi.Mcp.Server\u0027:check_origin/2"
            },
            {
              "name": "\u0027Elixir.AshAi.Mcp.Server\u0027:origin_allowed?/3"
            }
          ],
          "repo": "https://github.com/ash-project/ash_ai",
          "vendor": "ash-project",
          "versions": [
            {
              "lessThan": "28af68d73134df0b8fb3aa6ab03e8fd795b07c21",
              "status": "affected",
              "version": "c94f0b17fbe252f68755ba512678586164ba6139",
              "versionType": "git"
            }
          ]
        }
      ],
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "Origin Validation Error vulnerability in ash-project ash_ai allows a malicious web page to bypass the MCP server\u0027s DNS-rebinding protection and issue cross-site requests to a user\u0027s local MCP server with that user\u0027s actor.\n\nIn AshAi.Mcp.Server, with the default allowed_origins: nil, origin_allowed?/3 accepts an origin when uri.host == conn.host and the forwarded scheme is https. Both values are attacker-controlled: conn.host comes from the Host header and the scheme is read from the raw x-forwarded-proto header with no trusted-proxy check. Under DNS rebinding the browser sends the attacker\u0027s origin and a matching host, and page JavaScript may set X-Forwarded-Proto: https, so the check passes with no TLS or proxy involved. The fix trusts only localhost origins by default; other origins require an explicit allowed_origins allowlist.\n\nThis issue affects ash_ai: from 0.8.0 before 1.0.0."
    }
  ],
  "id": "CVE-2026-81315",
  "lastModified": "2026-09-01T21:15:00.147",
  "metrics": {
    "cvssMetricV40": [
      {
        "cvssData": {
          "Automatable": "NOT_DEFINED",
          "Recovery": "NOT_DEFINED",
          "Safety": "NOT_DEFINED",
          "attackComplexity": "LOW",
          "attackRequirements": "PRESENT",
          "attackVector": "NETWORK",
          "availabilityRequirement": "NOT_DEFINED",
          "baseScore": 7.4,
          "baseSeverity": "HIGH",
          "confidentialityRequirement": "NOT_DEFINED",
          "exploitMaturity": "NOT_DEFINED",
          "integrityRequirement": "NOT_DEFINED",
          "modifiedAttackComplexity": "NOT_DEFINED",
          "modifiedAttackRequirements": "NOT_DEFINED",
          "modifiedAttackVector": "NOT_DEFINED",
          "modifiedPrivilegesRequired": "NOT_DEFINED",
          "modifiedSubAvailabilityImpact": "NOT_DEFINED",
          "modifiedSubConfidentialityImpact": "NOT_DEFINED",
          "modifiedSubIntegrityImpact": "NOT_DEFINED",
          "modifiedUserInteraction": "NOT_DEFINED",
          "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
          "modifiedVulnConfidentialityImpact": "NOT_DEFINED",
          "modifiedVulnIntegrityImpact": "NOT_DEFINED",
          "privilegesRequired": "NONE",
          "providerUrgency": "NOT_DEFINED",
          "subAvailabilityImpact": "NONE",
          "subConfidentialityImpact": "NONE",
          "subIntegrityImpact": "NONE",
          "userInteraction": "ACTIVE",
          "valueDensity": "NOT_DEFINED",
          "vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
          "version": "4.0",
          "vulnAvailabilityImpact": "NONE",
          "vulnConfidentialityImpact": "HIGH",
          "vulnIntegrityImpact": "HIGH",
          "vulnerabilityResponseEffort": "NOT_DEFINED"
        },
        "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-81315",
          "options": [
            {
              "exploitation": "poc"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "total"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-08-31T16:02:11.016935Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-08-31T01:16:49.977",
  "references": [
    {
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
      "url": "https://cna.erlef.org/cves/CVE-2026-81315.html"
    },
    {
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
      "url": "https://github.com/ash-project/ash_ai/commit/28af68d73134df0b8fb3aa6ab03e8fd795b07c21"
    },
    {
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
      "url": "https://github.com/ash-project/ash_ai/security/advisories/GHSA-c92r-f3rr-q49h"
    },
    {
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
      "url": "https://osv.dev/vulnerability/EEF-CVE-2026-81315"
    },
    {
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
      "url": "https://github.com/ash-project/ash_ai/security/advisories/GHSA-c92r-f3rr-q49h"
    }
  ],
  "sourceIdentifier": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
  "vulnStatus": "Deferred",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-346"
        }
      ],
      "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
      "type": "Secondary"
    }
  ]
}

CVE-2026-81315 (GCVE-0-2026-81315)

Vulnerability from cvelistv5 – Published: 2026-08-31 00:57 – Updated: 2026-08-31 16:02

Title

MCP DNS-rebinding origin check in AshAi is bypassed by a spoofed X-Forwarded-Proto header

Summary

Severity

7.4 (High)


                        
                          CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

SSVC

Exploitation: poc Automatable: no Technical Impact: total

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-08-31 16:02 UTC

CWE

CWE-346 - Origin Validation Error

Assigner

EEF mitre root

References

4 references

URL	Tags
https://github.com/ash-project/ash_ai/security/ad…	vendor-advisoryrelated
https://cna.erlef.org/cves/CVE-2026-81315.html	related
https://osv.dev/vulnerability/EEF-CVE-2026-81315	related
https://github.com/ash-project/ash_ai/commit/28af…	patch

Impacted products

2 products

Vendor	Product	Version
ash-project	ash_ai	Affected: 0.8.0 , < 1.0.0 (semver) cpe:2.3:a:ash-project:ash_ai::::::::
ash-project	ash_ai	Affected: c94f0b17fbe252f68755ba512678586164ba6139 , < 28af68d73134df0b8fb3aa6ab03e8fd795b07c21 (git) cpe:2.3:a:ash-project:ash_ai::::::::

Credits

Peter Ullrich Peter Ullrich Zach Daniel / Ash Project Jonatan Männchen / EEF

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-81315",
                "options": [
                  {
                    "Exploitation": "poc"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "total"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-08-31T16:02:11.016935Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-08-31T16:02:38.700Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "references": [
          {
            "tags": [
              "exploit"
            ],
            "url": "https://github.com/ash-project/ash_ai/security/advisories/GHSA-c92r-f3rr-q49h"
          }
        ],
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "collectionURL": "https://repo.hex.pm",
          "cpes": [
            "cpe:2.3:a:ash-project:ash_ai:*:*:*:*:*:*:*:*"
          ],
          "defaultStatus": "unaffected",
          "modules": [
            "\u0027Elixir.AshAi.Mcp.Server\u0027"
          ],
          "packageName": "ash_ai",
          "packageURL": "pkg:hex/ash_ai",
          "product": "ash_ai",
          "programFiles": [
            "lib/ash_ai/mcp/server.ex"
          ],
          "programRoutines": [
            {
              "name": "\u0027Elixir.AshAi.Mcp.Server\u0027:check_origin/2"
            },
            {
              "name": "\u0027Elixir.AshAi.Mcp.Server\u0027:origin_allowed?/3"
            }
          ],
          "repo": "https://github.com/ash-project/ash_ai",
          "vendor": "ash-project",
          "versions": [
            {
              "lessThan": "1.0.0",
              "status": "affected",
              "version": "0.8.0",
              "versionType": "semver"
            }
          ]
        },
        {
          "collectionURL": "https://github.com",
          "cpes": [
            "cpe:2.3:a:ash-project:ash_ai:*:*:*:*:*:*:*:*"
          ],
          "defaultStatus": "unaffected",
          "modules": [
            "\u0027Elixir.AshAi.Mcp.Server\u0027"
          ],
          "packageName": "ash-project/ash_ai",
          "packageURL": "pkg:github/ash-project/ash_ai",
          "product": "ash_ai",
          "programFiles": [
            "lib/ash_ai/mcp/server.ex"
          ],
          "programRoutines": [
            {
              "name": "\u0027Elixir.AshAi.Mcp.Server\u0027:check_origin/2"
            },
            {
              "name": "\u0027Elixir.AshAi.Mcp.Server\u0027:origin_allowed?/3"
            }
          ],
          "repo": "https://github.com/ash-project/ash_ai",
          "vendor": "ash-project",
          "versions": [
            {
              "lessThan": "28af68d73134df0b8fb3aa6ab03e8fd795b07c21",
              "status": "affected",
              "version": "c94f0b17fbe252f68755ba512678586164ba6139",
              "versionType": "git"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:a:ash-project:ash_ai:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "1.0.0",
                  "versionStartIncluding": "0.8.0",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ],
          "operator": "AND"
        }
      ],
      "credits": [
        {
          "lang": "en",
          "type": "finder",
          "value": "Peter Ullrich"
        },
        {
          "lang": "en",
          "type": "reporter",
          "value": "Peter Ullrich"
        },
        {
          "lang": "en",
          "type": "remediation developer",
          "value": "Zach Daniel / Ash Project"
        },
        {
          "lang": "en",
          "type": "coordinator",
          "value": "Jonatan M\u00e4nnchen / EEF"
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "supportingMedia": [
            {
              "base64": false,
              "type": "text/html",
              "value": "\u003cp\u003eOrigin Validation Error vulnerability in ash-project ash_ai allows a malicious web page to bypass the MCP server\u0027s DNS-rebinding protection and issue cross-site requests to a user\u0027s local MCP server with that user\u0027s actor.\u003c/p\u003e\n\u003cp\u003eIn \u003ccode\u003eAshAi.Mcp.Server\u003c/code\u003e, with the default \u003ccode\u003eallowed_origins: nil\u003c/code\u003e, \u003ccode\u003eorigin_allowed?/3\u003c/code\u003e accepts an origin when \u003ccode\u003euri.host == conn.host\u003c/code\u003e and the forwarded scheme is \u003ccode\u003ehttps\u003c/code\u003e. Both values are attacker-controlled: \u003ccode\u003econn.host\u003c/code\u003e comes from the \u003ccode\u003eHost\u003c/code\u003e header and the scheme is read from the raw \u003ccode\u003ex-forwarded-proto\u003c/code\u003e header with no trusted-proxy check. Under DNS rebinding the browser sends the attacker\u0027s origin and a matching host, and page JavaScript may set \u003ccode\u003eX-Forwarded-Proto: https\u003c/code\u003e, so the check passes with no TLS or proxy involved. The fix trusts only localhost origins by default; other origins require an explicit \u003ccode\u003eallowed_origins\u003c/code\u003e allowlist.\u003c/p\u003e\n\u003cp\u003eThis issue affects ash_ai: from 0.8.0 before 1.0.0.\u003c/p\u003e"
            },
            {
              "base64": false,
              "type": "text/markdown",
              "value": "Origin Validation Error vulnerability in ash-project ash_ai allows a malicious web page to bypass the MCP server\u0027s DNS-rebinding protection and issue cross-site requests to a user\u0027s local MCP server with that user\u0027s actor.\n\nIn `AshAi.Mcp.Server`, with the default `allowed_origins: nil`, `origin_allowed?/3` accepts an origin when `uri.host == conn.host` and the forwarded scheme is `https`. Both values are attacker-controlled: `conn.host` comes from the `Host` header and the scheme is read from the raw `x-forwarded-proto` header with no trusted-proxy check. Under DNS rebinding the browser sends the attacker\u0027s origin and a matching host, and page JavaScript may set `X-Forwarded-Proto: https`, so the check passes with no TLS or proxy involved. The fix trusts only localhost origins by default; other origins require an explicit `allowed_origins` allowlist.\n\nThis issue affects ash_ai: from 0.8.0 before 1.0.0."
            }
          ],
          "value": "Origin Validation Error vulnerability in ash-project ash_ai allows a malicious web page to bypass the MCP server\u0027s DNS-rebinding protection and issue cross-site requests to a user\u0027s local MCP server with that user\u0027s actor.\n\nIn AshAi.Mcp.Server, with the default allowed_origins: nil, origin_allowed?/3 accepts an origin when uri.host == conn.host and the forwarded scheme is https. Both values are attacker-controlled: conn.host comes from the Host header and the scheme is read from the raw x-forwarded-proto header with no trusted-proxy check. Under DNS rebinding the browser sends the attacker\u0027s origin and a matching host, and page JavaScript may set X-Forwarded-Proto: https, so the check passes with no TLS or proxy involved. The fix trusts only localhost origins by default; other origins require an explicit allowed_origins allowlist.\n\nThis issue affects ash_ai: from 0.8.0 before 1.0.0."
        }
      ],
      "impacts": [
        {
          "capecId": "CAPEC-62",
          "descriptions": [
            {
              "lang": "en",
              "value": "CAPEC-62 Cross Site Request Forgery"
            }
          ]
        }
      ],
      "metrics": [
        {
          "cvssV4_0": {
            "Automatable": "NOT_DEFINED",
            "Recovery": "NOT_DEFINED",
            "Safety": "NOT_DEFINED",
            "attackComplexity": "LOW",
            "attackRequirements": "PRESENT",
            "attackVector": "NETWORK",
            "baseScore": 7.4,
            "baseSeverity": "HIGH",
            "privilegesRequired": "NONE",
            "providerUrgency": "NOT_DEFINED",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "NONE",
            "subIntegrityImpact": "NONE",
            "userInteraction": "ACTIVE",
            "valueDensity": "NOT_DEFINED",
            "vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N",
            "version": "4.0",
            "vulnAvailabilityImpact": "NONE",
            "vulnConfidentialityImpact": "HIGH",
            "vulnIntegrityImpact": "HIGH",
            "vulnerabilityResponseEffort": "NOT_DEFINED"
          },
          "format": "CVSS",
          "scenarios": [
            {
              "lang": "en",
              "value": "GENERAL"
            }
          ]
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-346",
              "description": "CWE-346 Origin Validation Error",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-31T00:57:55.910Z",
        "orgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
        "shortName": "EEF"
      },
      "references": [
        {
          "tags": [
            "vendor-advisory",
            "related"
          ],
          "url": "https://github.com/ash-project/ash_ai/security/advisories/GHSA-c92r-f3rr-q49h"
        },
        {
          "tags": [
            "related"
          ],
          "url": "https://cna.erlef.org/cves/CVE-2026-81315.html"
        },
        {
          "tags": [
            "related"
          ],
          "url": "https://osv.dev/vulnerability/EEF-CVE-2026-81315"
        },
        {
          "tags": [
            "patch"
          ],
          "url": "https://github.com/ash-project/ash_ai/commit/28af68d73134df0b8fb3aa6ab03e8fd795b07c21"
        }
      ],
      "source": {
        "discovery": "EXTERNAL"
      },
      "title": "MCP DNS-rebinding origin check in AshAi is bypassed by a spoofed X-Forwarded-Proto header"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
    "assignerShortName": "EEF",
    "cveId": "CVE-2026-81315",
    "datePublished": "2026-08-31T00:57:55.910Z",
    "dateReserved": "2026-08-30T20:00:01.860Z",
    "dateUpdated": "2026-08-31T16:02:38.700Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

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.